Circle Track Analyzer v3.6 for Windows User`s Manual

Circle Track Analyzer v3.6 for Windows User`s Manual
Circle Track
Analyzer v3.6
for Windows
User’s Manual
Performance Trends, Inc.
2
Performance Trends, Inc. PO Box 530264, Livonia, MI 48153
Sales & Tech Help for Registered Owners (248) 473-9230 Fax: 248-442-7750
Email: [email protected]
Website (tips, correspond with other users, download demos, update schedule, etc.)
www.performancetrends.com
Copyright Notice
Copyright (C) 2009 Performance Trends, Inc.
All Rights Reserved
These software programs and user's manual are reserved by Performance Trends, Inc. and are intended
for the use of the original owner only. Copying or duplicating these products except for the personal use
of the original owner is a violation of U. S. Copyright Law and is hereby expressly forbidden.
Portions Copyright (C) Microsoft Corp. 1993
All Rights Reserved
International Business Machines Corp. makes no warranties, either expressed or implied, regarding the
enclosed computer package, its merchantability or its fitness for any particular purpose.
IBM PC, XT, and AT are registered trademarks of International Business Machines Corp.
MS-DOS is a registered trademark of Microsoft Corp.
DISCLAIMER OF WARRANTIES:
THE SOFTWARE PROVIDED HEREUNDER IS LICENSED "AS IS" WITHOUT ANY
WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO, ANY
WARRANTIES FOR MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. NO
ORAL OR WRITTEN STATEMENTS, REPRESENTATIONS OR OTHER AFFIRMATION OF
FACT, INCLUDING BUT NOT LIMITED TO STATEMENTS REGARDING CAPABILITY,
CAPACITY, SUITABILITY FOR USE OR PERFORMANCE OF SOFTWARE SHALL BE RELIED
UPON BY USER OR BE DEEMED TO BE A WARRANTY OR REPRESENTATION BY
PERFORMANCE TRENDS, INC. FOR ANY PURPOSE, OR GIVE RISE TO ANY LIABILITY OF
OBLIGATION OF PERFORMANCE TRENDS, INC. WHATSOEVER. USER ACCEPTS ALL
RESPONSIBILITY FOR SELECTING THE SOFTWARE TO MEET USER NEEDS OR SPECIFIC
PURPOSES. PERFORMANCE TRENDS INC. IS UNDER NO OBLIGATION TO FURNISH USER
UPDATES OR ENHANCEMENTS EVEN IF FURNISHED TO OTHER
USERS.
Continued on next page.
3
LIMITATION Of LIABILITY:
If at the time of delivery to the original User only there are any defects in the media on which the
Software is provided, User's sole and exclusive remedy shall be the replacement of any media returned to
Performance Trends, Inc. within 90 days of the receipt of the Software by User, or at Performance Trends
Inc.'s sole option, a refund of the License fees paid to Performance Trends, Inc. by User.
IN NO EVENT SHALL PERFORMANCE TRENDS, INC. OR THIRD PARTIES WHO HAVE
RIGHTS IN THE SOFTWARE BE LIABLE TO USER FOR LOSS OF PROFITS, INDIRECT,
SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES EVEN IF PERFORMANCE TRENDS,
INC. IS AWARE OF THE POSSIBILITY OF SUCH DAMAGES.
IN THE EVENT ANY REMEDY HEREUNDER FAILS OF ITS ESSENTIAL PURPOSE, OR IN ANY
OTHER EVENT, PERFORMANCE TRENDS INC.'S LIABILITY HEREUNDER SHALL NOT
EXCEED ANY AMOUNTS PAID BY USER TO PERFORMANCE TRENDS, INC. UNDER THIS
AGREEMENT.
Some states do not allow the limitation or exclusion of liability for incidental or consequential damages
and some states do not allow the exclusion of implied warranties, so the above limitations or exclusions
may not apply to you.
No action, regardless of form, arising out of any claimed breach of this agreement or performance under
this agreement may be brought by either party more than one year after the affected party learns of the
cause of action.
Refer to diskette envelope for full license agreement.
********************************** W A R N I N G ***********************************
The Circle Track Analyzer makes calculations based on equations and data found in various published
and heretofore reliable documents. The program is designed for use by skilled professionals experienced
with engines and vehicles. The following processes are hazardous, particularly if done by an unskilled or
inexperienced user:
-
Obtaining data to input to the program
Interpreting the program's results
Before making measurements of or modifications to any vehicle, engine or driving situation, DO NOT
FAIL TO:
4
Regard the safety consequences
Consult with a skilled and cautious professional
Read the entire user's manual
Obey all federal, state & local laws
Respect the rights and safety of others
Table of Contents
Chapter 1 Introduction
1.1 Overview of Features
1.2 Before You Start
1.3 A Word of Caution
1.4 Getting Started (Installation)
1.5 Example to Get You Going
Chapter 2 Definitions
2.0 Basic Program Operation
2.1 Preferences
2.2 Engine
2.3 Vehicle
2.4 Front Suspension
2.5 Rear Suspension
2.6 Calculated Lap Times (Performance)
2.6.1 Running Conditions
2.6.2 Calculate Performance Test Results
2.7 Calculation Menus
2.8 Match My Lap Times
Chapter 3 Output
3.0 Test Results
3.1 Analyze Perf. Reports
3.2 Graphs
3.3 Vehicle (& File) Library
3.4 Printer Output
3.5 History Log
3.6 Analyze Suspension
1
1
2
3
4
5
11
11
13
14
19
27
48
59
59
65
70
90
93
93
95
97
106
110
112
116
5
Chapter 4 Examples
125
Example 4.1
Finding the Best Axle Ratio
127
Example 4.2
Calibrating Circle Track Analyzer
for Your Car
138
Analyzing the Front Suspension
153
Example 4.3
Appendix 1: Accuracy and Assumptions
165
Appendix 2: General Tips
169
Appendix 3: New Features in v3.2
174
Appendix 4: New Features in v3.5
179
Appendix 5: New Features in v3.6
191
Index
199
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Circle Track Analyzer
Chapter 1 Introduction
Chapter 1 Introduction
1.1 Overview of Features
The Circle Track Analyzer program by Performance Trends, Inc. is a software system to let circle track
racers, performance enthusiasts, and even the average driver understand and predict many aspects circle
track racing and vehicle handling. The Circle Track Analyzer, Version 2 has been designed to be easier,
faster and more accurate. Several new features have been added and other features enhanced. The major
changes in Circle Track Analyzer Version 2 are listed below:
New Features:
•
•
•
•
•
•
•
•
•
•
•
•
Mouse driven user interface compatible with Windows 98 through Vista for easier operation and
better print capability.
Improved Front Suspension layout screen, very similar to our popular Roll Center Calculator.
Rear Suspension layout screen, for simple analysis of rear suspensions.
Improved suspension and analysis screen to watch front suspension motion while traveling around
the track.
Feature to automatically pick the best gear at a particular track.
Feature which allows the program to adjust critical specs to best match your lap times and highest
and lowest vehicle RPMs at a particular track.
Can print most menus and calculation menus separately.
Keeps log of last 25 tests run, for comparison or recall. You can also select to save up to 10 of these
tests for as long as you wish. You can also select to graph up to 5 of these tests with the current
results.
Advanced file Open and Save commands let you access any drive or directory with standard
Windows File Dialog menu.
Better printing of reports.
Ability to graph the results. These graphs include many options like zoom, shift, line styles, etc.
On screen help by simply clicking on any input spec.
If you require more detailed analysis or more features, you may need our upcoming Circle Track
Analyzer "Pro".
Check Appendices 3-5, pages 165-198 for Features added in Versions 3.2, 3.5 and 3.6.
Also, v3.6 can be “unlocked” into 3 different versions, just Roll Center Calculator v3.6
(front suspension only), just Roll Center Calculator Plus v3.6 (front and rear suspension),
and the Full Circle Track Analyzer v3.6.
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Circle Track Analyzer
Chapter 1 Introduction
1.2 Before You Start
What you will need:
•
•
•
•
128 Meg of RAM.
Approximately 8 Megabyte of disk space.
Windows 98, Me, XP, 2000, NT, Vista
Printer (optional).
Many terms used by the Circle Track Analyzer and this user's manual are similar to terms used by other
publications, like Roll Center, Tire Traction Factor, etc. However, these terms may have different
definitions. Therefore, read Chapter 2 to see what these terms mean to the Circle Track Analyzer.
Occasionally it will be necessary to identify "typos" in the manual, known "bugs" and their "fixes", etc.
which were not known at the time of publication. These will be identified in a file called
README.DOC in the Circle Track Analyzer directory or folder.
To read this file, use Windows Explorer to find the Circle Track Analyzer directory, usually
CTA20 under PERFTRNS.PTI. Then double click on README.DOC. Wordpad will display
the contents.
A new feature has been added to read the README.DOC file from inside the Circle Track Analyzer
program. At the main screen, click on Help from the Menu bar, then select “View README.DOC
File”.
Every effort has been made by Performance Trends, Inc to provide you with an accurate, cost saving,
high quality tool at a very reasonable price. We do not copy protect our software, to allow our customers
full freedom to make back-up copies for their own personal use. Please respect the programmer's
copyright and do NOT give out copies to your friends.
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Chapter 1 Introduction
1.3 A Word of Caution
The Circle Track Analyzer is a comprehensive software package which estimates a vehicle's performance
based on limited user input. These estimates can be used for analysis of circle track performance. A
vehicle is a very complex system, which makes exact calculations of all details impossible. Therefore,
several simplifying assumptions are made to reduce the calculations to a manageable level. See the
Assumptions in Appendix 1. The user must recognize:
The software can not predict the safety of a vehicle modification or driving situation. Done
correctly, with the proper quality parts and safety precautions, extreme vehicle conditions can be
safe. Done by inexperienced racers with standard or low quality parts, a race car can be a "disaster
waiting to happen". Please read and follow the "Safety Notes" as highlighted in this manual.
The software, like any computer model, can NOT make exact predictions because:
• Much of the input data to the software is estimated.
• Even if the input data were exactly correct, the simplifying assumptions within the program will
limit the accuracy.
• Environmental conditions, driver performance, track conditions, etc. are rarely constant and
repeatable.
The software should be used as a guide to:
• Help you understand how an vehicle works; what parameters are important, how parameters
interact, what are the tradeoffs, etc.
• Point you in the correct, general direction for making modifications. This direction should be
verified by other sources like known authorities, race results, books, etc. Never trust one "single
source" if it does not make sense to you.
• Make you think, not think for you. If unexpected results are obtained, take a minute to:
• Double check all your data input.
• Refer back to this manual.
• Ask someone else skilled and experienced in the particular area.
• Give the retailer or Performance Trends Inc's. Tech Help Line a call for an explanation.
(Computer programs are written by normal people who can make mistakes. It's always
possible there may be an error in the calculations. Your phone call may help us correct
it.)
Please also read the Warranty and Warning at the beginning of this manual and on the diskette envelope.
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Chapter 1 Introduction
1.4 Getting Started (Installation)
You must install the Circle Track Analyzer from the distribution CD. To do this, simply place the CD in
the CD drive and it will auto-start the Performance Trends Installation Wizard. From this Wizard, you
can select to install any of our products as demos, or the Circle Track Analyzer (which is not a demo).
The button to install Circle Track Analyzer will be highlighted, probably in the color green. Just click on
this button to start the installation, then follow the instructions in the installation program.
Figure 1.0 Installation Wizard
For most users, just
click on OK for each
question asked to accept
the default answers
suggested by the
Installation program.
Once you have installed
the Circle Track
Analyzer, there should
be a Circle Track
Analyzer icon on your
desktop for you to click
on. Otherwise, use
Windows Explorer to
find the CTA20 folder
Click here to install
(directory) under the
PERFTRNS.PTI folder
(directory) and click on
the CTA.EXE program. (Version 3.6 is installed in the C:\Program Files\Performance Trends\Circle
Track Analyzer v3.6 folder.)
Entering Registered Owner's Name:
During your first setup, the Circle Track Analyzer will ask you to enter your name as the Registered
Owner. During this first session, you can modify it until you are satisfied. Once you accept the name,
the computer will generate a code # based on the name. To be eligible for Tech Help, you will need both
your registered name and code #, and to have sent in your registration card. The name you enter should
be very similar to the name you enter on the registration card.
Click on About in the Main Menu to review your name and code # .
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Chapter 1 Introduction
1.5 Example to Get You Going
To start the Circle Track Analyzer from Windows 3.1, click on the Circle Track Analyzer icon in the
Perf.Trnds program group. From Windows 95 or 98, click on Start, then Programs, then Perf. Trends,
and then Circle Track Analyzer. After some brief introduction screens, you will be left at the Main Menu
shown below.
Figure 1.1 Main Menu
LATEMODL
is name of
Vehicle
Specs
currently
being
worked with
Click here
to display
all vehicle’s
saved in
Vehicle
Library
Click here
to display
the menu
shown in
Figure 1.2
From this main menu, you can:
•
•
•
•
•
Choose to review or modify any of the categories of vehicle specifications displayed.
Open or Save a file of complete vehicle specifications by clicking on the Open or Save buttons (first
2 buttons on the left) or the File menu item, then either Open or Save.
Add, edit or review vehicle comments to describe the vehicle currently held in the program.
Calculate vehicle performance from the options listed under Running Conditions. From here you
can specify calculation options (weather conditions, track specs, driver types, etc.).
Change the Preferences options to somewhat customize the program for you.
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•
•
Circle Track Analyzer
Chapter 1 Introduction
Get HELP to explain these options by clicking on Help or pressing <F1>.
Quit the program by clicking on File, then Exit, or click on the Quit button.
All these options are explained in detail in Chapters 2 and 3.
In the Main Menu’s blue title bar you will notice the current Vehicle is [LATEMODL]. The program has
descriptions of vehicles saved in the Library right from the factory. The current file from the Vehicle
Library is called LATEMODL.
To get started, let's examine (but not change) the various categories of specs. Click on a button for one
of the categories like Engine, Vehicle, etc. A new menu will appear displaying the various specs and the
current values for the LATEMODL vehicle. You can click on the name of any spec and a brief
description appears in the Help frame, along with a page # from this manual for more help. You can
return to the Main Menu by clicking on OK or clicking on an area outside this menu.
Now click on the Calculate Performance button in the Main Menu to calculate performance for this
LATEMODL vehicle. The next menu will show you the Calculate Performance Conditions menu as
shown in Figure 1.2.
For now, leave all the Calculation Conditions as they are and click on the Calculate Performance button.
This will start the program calculating performance for the specifications of the LATEMODL stored in
Figure 1.2, Calculation Conditions Menu
Click here to
calculate Lap
Time
performance
shown in
Figure 1.3
the Vehicle Library with the Calculation Conditions currently displayed. A progress bar graph shows
how the calculations are progressing. The calculations may require several seconds on slower computers.
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Chapter 1 Introduction
The final results will appear in a table as in Figure 1.3. The columns are for various types of readings
(Time, MPH, etc) which occurred at even time intervals during the run. The results contain much
information, some which may not be familiar to you. However, if you look at the Results Summary in
the upper right corner, you see a lap time of 16.12 seconds with an average speed of 83.7 MPH. These
are results you do understand.
If you click on the slide bar button identified in Figure 1.3, and slide the results down to the last row of
results, you see a time 8.06 seconds, exactly half of the Lap Time of 16.12 seconds. That is because the
program only calculates half of a lap, from turn 2 through the straight through turn 3. The program then
assumes the other half lap would be exactly the same and just doubles the time for half a lap.
Figure 1.3 Calculated Results with Lap Time
Results
Summary
Click on slide
bar and slide
button down
to see all test
results.
Summary of
important
Notes of
Interest. Click
on Notes
button for
more info.
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Circle Track Analyzer
Chapter 1 Introduction
Figure 1.4, Calculated Results with Help Definition
Click here or press
the F1 key for
general help on what
your options are at
this point in the
program.
By clicking on a
number in the
results, an
explanation and
definition is given,
including a page
number in this
manual for more
information.
The menu bar and the command buttons at the top of the screen shows some of the options for
various formats for data output:
•
•
•
•
Analyze Perf will produce a report of performance and safety tips on the test results
Analyze Suspension will show the car traveling around the track and how the corner weights and
front suspension members are changing.
Graph will produce various types of graphs. You can also compare the current results to results of
the previous run, or some other Baseline you have saved.
Print lets you print these results on your printer.
If you have a printer hooked up to your computer, try the Print command by clicking on Print in the
menu bar or on the Printer button. A small menu of printout options are presented. These options allow
you to enter a report comment, include vehicle specs and comments in the printout, etc. These options
are explained in Section 3.4. For this first time, accept the default settings and print the report by
clicking on Print Results.
To help explain the other columns of output, simply click on those results. A definition of that particular
data will be presented in a Message box as in Figure 1.4. Then click on OK when you have read the
definition.
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Chapter 1 Introduction
For a detailed explanation of all the results, Calculation Conditions, and output options, go to Section 2.6
and Chapter 3.
Clicking on Back or pressing the <ESC> key will return you to the Main Menu. From the Main Menu
you can modify the LATEMODL to see the effect on performance. For example you could go into any
of the component menus and:
•
•
•
Change to a different rear axle ratio.
Install ‘stickier’ tires.
Change weather or driving conditions.
The beauty of the program is that it repeats exactly each time. This lets you find differences which
would be “clouded” by changes in track conditions or driver variations.
Many of the input specifications you see in the various menus may not be familiar to you. For a brief
definition of the inputs, simply click on the specification name. The definition will appear in the Help
frame with a page # in this manual for more info.
Some of the vehicle specifications have “Clc” buttons. One example is Dew Point in the Calculate
Performance Conditions menu. “Clc” stands for "calculate". For example, if you want to calculate the
Dew Point from wet and dry bulb readings, simply click on the Clc button. The program will display a
new menu listing the inputs and the Calc Dew Point from these inputs. For further explanation, click on
the Help buttons in these menus. To use the Calc Dew Point calculated from these inputs, click on the
Use Calc Value button. Otherwise click on Cancel to return to the Calculate Performance Conditions
menu with no change to Dew Point. Section 2.8, Calculation Menus explains all these calculations.
Once you feel comfortable changing specifications in the various menus and making various performance
calculations, read Section 3.3 of this manual called Vehicle Library to learn how to save a set of vehicle
specifications or recall information which has been previously saved. Then you will know all the basic
commands to operate the program. For a more in-depth knowledge of using these commands and an
explanation of the results, read this entire manual.
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Circle Track Analyzer
Chapter 1 Introduction
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Circle Track Analyzer
Chapter 2 Definitions
Chapter 2 Definitions
2.0 Basic Program Operation:
Figure 2.1 shows the Circle Track Analyzer’s Main Menu with explanations of your options here.
Figure 2.1 Main Menu Options
Buttons to display
individual menus
containing vehicle
and driving specs.
Menu bar. Click here for “drop down”
menus of program options, some being
the same as the Command Buttons.
Name of current vehicle file
Command
buttons to
Save or Open
a vehicle file,
calculate
performance,
and perform
other special
calculations
This area gives
a general
description or
summary of
each of the 4
menus of
specs which
make up a
vehicle
Enter comments to describe vehicle
Click here to display Running Conditions (weather, track length, etc), and
then calculate performance.
Move mouse over an area and a description of the item is given here
V3.6 can be “unlocked” into 3 different versions, just Roll Center Calculator (front
suspension only), just Roll Center Calculator Plus (front and rear suspension), and the
Full Circle Track Analyzer v3.6. This can significantly change the appearance of the Main
Screen. Check Appendix 5, page 191.
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Circle Track Analyzer
Chapter 2 Definitions
Figure 2.2 shows the Engine menu with explanations of options for most component menus.
Figure 2.2 Explanation of Sections of Typical Menu
Name of specs. Click on them for a description in the menu’s help frame.
Help frame giving definition of spec and page # in manual for more info.
Drop down combo box. Click on down arrow button on the right
side to pick from a list of possible choices for this spec.
Standard text entry box where you can type in the value of
the spec (which will be checked against acceptable limits).
Calculation button which opens up another
menu where you can calculate the value of
a spec from other inputs
Click on commands in the menu bar to:
• Exit this menu
• Open (retrieve) a set of example engine specs provided by
Performance Trends, or a set of specs you have previously saved.
• Print this screen.
• Import an Engine Analyzer power curve.
• Display the Engine Comments with other comments describing this
vehicle and front & rear suspension.
• Calculate a power curve from simple inputs.
• Obtain further help on this screen.
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Chapter 2 Definitions
2.1 Preferences
Click on the Preferences item in the menu bar at
the top of the Main Menu screen to drop down the
Preferences shown in Figure 2.3. Here you can
adjust some program items to personalize the
program for your needs.
Figure 2.3 Preferences Menu
Available from Main Menu
Beginner/Experienced Level
If you select Beginner, the program will lock out
the more complicated features, make more checks
on specs assuming you could be making mistakes,
and gives more explanation before an action is performed (assuming you may not be familiar it). We
strongly recommend this choice to anyone new to computers or this program.
Engine Graph - Thick Lines
Engine Graph - Thin Lines
Lets you customize the way the Full Power Curve graph in the Engine specs menu is displayed and
printed.
Restart Displaying Help Tips
You will notice several tips displayed during running the program, many with a Check Box which says
“Don’t Show This Again”. Once you are aware of a tip, you do not want to be shown it again, so click
on this check box to “X” it, then click on OK.
If you ever want to review a tip, click on this menu item, and all tips will be displayed again at the
appropriate time in the program, just as when the program was new, before you checked “Don’t Show
This Again”.
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Chapter 2 Definitions
2.2 Engine
The Engine specs describe the engine's size in cubic inches, its torque and HP, and what power correction
was used for rating the engine’s torque and HP.
Figure 2.4 Engine Specs Menu (shown with Full Power Curve)
Click on File, then:
• New to blank out the power curve table.
• Open Example to pick an example engine provided with the program.
• Save to save these engine specs to a name of your choosing.
• Print or Windows Printer Setup to print this screen.
• here to set the amount of detail you want to give the program about the
power curve
Name of
current set
of Engine
Specs. You
give the
specs a
name when
you save
then
Torque and
HP graph
based on
data in table
below it.
Note that
HP has a
separate
scale on the
right side.
Click here to load a power curve from an Engine
Analyzer program
Click here or here to calculate power curve specs from other simple inputs.
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Chapter 2 Definitions
Displacement, cu in
The engine’s cubic inch displacement is used to estimate the amount of rotating inertia * in the engine
and clutch/flywheel or converter. Because this spec has a Clc button, Displacement can be calculated
from other inputs. See Section 2.7.2. The bigger the cubic inches, the larger the assumed rotating inertia.
* Definition of Engine Inertia: The engine inertia is a measure of how massive the engine's rotating
components are and how difficult it is to accelerate or decelerate the engine itself. Most of the
engine's inertia is contained in the flywheel/clutch assembly for a manual transmission, or in the
torque converter for an automatic transmission. The more massive or the larger the diameter the
flywheel or any rotating engine component, the larger the inertia value.
Under this input, the engine’s displacement is shown for CCs and Liters.
Clutch
Click on the down arrow button to pick a general description of the clutch and flywheel used with this
engine. This choice will only affect the rotating Engine Inertia the program assumes. The larger the
clutch and flywheel, the more the engine inertia. See Displacement above.
Power Curve Data
There are several ways to load in RPM, torque and HP data into the table on the right side of the Engine
menu. You can:
• Pick an Example dyno curve supplied by Performance Trends by clicking on File, the Open
Example Engine.
• Pick a set of specs you have previously saved by clicking on File, the Open Saved Engine.
• Calculate one based on simple inputs by clicking on Calculate in the Menu at the top.
• Load an Example curve, you can load a curve calculated from one of our Windows Engine
Analyzer Programs
• Simply type in readings as from a dyno curve. If you type in readings, as soon as there 2 readings
for any set of 3 inputs, the 3rd one is automatically calculated and filled in, and the new point is
added to the graph.
The graph always shows a sharp drop in power after the highest RPM point in the table. This is to
remind you that this is what the program assumes for calculations, that engine power drops significantly
(like it ran into an overspeed) after the highest RPM. If you want the power to not drop so suddenly, then
you must add an additional RPM above your current highest RPM, and enter a HP reading which draws
the curve like you expect it to look.
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Chapter 2 Definitions
The Circle Track Analyzer assumes all torque and HP numbers entered are recorded at a steady RPM
(not accelerating) and corrected to the aftermarket dynamometer standard correction factor.
Dynamometers which mostly test racing engines (typical of magazine articles and aftermarket testing
companies) generally correct their data to 29.92" Hg, 60 degrees F and approximately 0 degrees F dew
point (no humidity).
Menu Commands
The menu bar at the top provides for several command options, some which are fairly self explanatory:
• Back returns you to the main menu.
• File opens up several typical Windows options:
• New will blank out all the RPM, torque and HP entries, Displacement, Clutch Type, Engine
Comments; and the Engine File name will be called “Untitled”.
• Open Example Engine File will open a typical Circle Track Analyzer “File Open” menu, where
you can pick a set of example Engine Specs loaded by Performance Trends.
• Open Saved Engine File will open a typical Circle Track Analyzer “File Open” menu, where
you can pick a set of Engine Specs which you have saved, using the Save command in this
menu.
• Save Engine File will open a typical Circle Track Analyzer “File Save” menu, where you can
save the current set of Engine Specs and Engine Comments under a name of your choosing.
This name then appears at the top of the Engine Specs menu. This name should not be
confused with the Vehicle Name which appears at the top of the main screen. The Vehicle
Name includes the engine specs, and therefore the Engine Name.
• Print lets you print this screen.
• Windows Printer Setup lets you change printer selection, paper orientation, etc.
• Calculate will calculate a power curve from simple inputs. See Section 2.7.1 on this Calculation
Menu.
• The Load from Engine Analyzer command will be discussed in more detail below.
• Help brings up a series of help screens on the Engine Specs menu.
Load from Engine Analyzer
The Circle Track Analyzer can load engine power curves created by the proper Windows versions of
Engine Analyzer EZ, the standard Engine Analyzer, and Engine Analyzer Pro.
Generally you will start this process by running the Engine Analyzer program first. Once the Calculated
Performance results have been calculated and displayed on the screen, click on the Send button in the
Engine Analyzer. This Engine Analyzer menu looks similar to Figure 2.5. It will ask what program do
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Chapter 2 Definitions
you want to send the power curve to, where you could click the Circle Track Analyzer option. There are
other options which you can refer to your Engine Analyzer manual.
The process of loading Engine Analyzer results into Circle Track Analyzer is nearly automatic and
consists of:
1. Once you’ve selected the Circle Track Analyzer as the program to Send the results to, click on
the OK/Send button in the Engine Analyzer’s Send menu to leave the Engine Analyzer.
2. The Circle Track Analyzer will be automatically activated and run.
3. When the Circle Track Analyzer stars up the first time, you are given notice that a power curve
is available and can be loaded from the Engine specs menu. You will also notice some new
commands on the Main Menu called “Engine Analyzer”. Clicking on these will return to
control to the Engine Analyzer program which originally called the Circle Track Analyzer, but
will leave the Circle Track Analyzer also running, ready for a new power curve.
4. Important: Once you load the power curve, the old power curve is gone, unless you saved the
vehicle specs including power curve with the Save command or saved it as an Example by
clicking on the Save Example button at the Engine specs menu.
5. When you are ready to return to the Engine Analyzer, simply click on one of the Engine
Analyzer buttons (at the Main Menu or in the Test Results screen) or commands in the Menu
bar. You do not have to load the power curve. You can jump between the Engine Analyzer and
Circle Track Analyzer as many times as you want.
If an Engine Analyzer program is not
currently running and “talking” to the
Circle Track Analyzer, you can also start
the process by clicking on the Load from
Engine Analyzer menu command. You
will get the screen of Figure 2.5.
Figure 2.5 Menu to Start Up an Engine
Analyzer Program
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Chapter 2 Definitions
Troubleshooting
If this process of loading power curves into the Circle Track Analyzer from the Engine Analyzer does
not work like described above, consider the following.
• You do not own the correct Windows version of Engine Analyzer program.
• You have renamed the Circle Track Analyzer or Engine Analyzer executable (.EXE) file. The
Circle Track Analyzer should be CTA.EXE.
• In the Engine Analyzer program, click on the “Look for It” button by the Circle Track Analyzer
option to see if the program can find a correct Windows version.
• You are trying to help the programs transfer control to each other. Do not minimize one of the
programs, then activate the other program as this can confuse the process.
Figure 2.6 Optional Engine Analyzer Send Screen To Tell Where Circle
Track Analyzer is Located (required for some early Engine Analyzers)
Click on Send in an Engine
Analyzer program to bring up
this screen
Select the ‘Other’ Option
Type in CTA as the Program
Name
Type in the Full Path where
the CTA program is located,
usually C:\perftrns.pti\cta20
Program Icon Name is CTA
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Chapter 2 Definitions
2.3 Vehicle Specs
The Vehicle specs describe transmission's efficiency, gear ratios, vehicle size, weight, weight
distribution, final drive system, tires and aerodynamics.
Figure 2.7 Vehicle Specs Menu
General Vehicle specs. Click on
the Clc buttons to calculate
inputs from other info, like weight
%s from 4 corner weights.
Tire specs have a large effect on
traction, cornering ability and therefore
lap times, especially on short tracks
Transmission specs affect engine RPM
range and power losses (efficiency).
Click here to print this screen.
Aerodynamic specs usually do not have a large effect until vehicle
speeds start to exceed 100 MPH.
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Chapter 2 Definitions
General Vehicle Specs
Total Weight with Driver, lbs
Total vehicle weight in pounds with the driver, ballast, and the amount of fuel you want to analyze.
% Rear
% Left
% Cross
These 3 specs describe the vehicle's weight distribution, indicating the % of the vehicle's total weight
which is on the rear tires, on the left tires, and the right front + left rear tires. A typical street car (same
suspension left and right) are designed for having 50% Left and 50% Cross weight, and only perhaps
42% Rear.
Note that the result of these weight percents combined with the Vehicle Weight are displayed as the
corner weights next to these inputs. If you know your car’s corner weights but not the percents, click on
one of the Clc (calculation) buttons to calculate these percents. See Section 2.7.3.
Height of CG
Describes the height of the vehicle's
center of gravity from level ground.
A sports car will have a lower CG
than a 4WD truck. Increasing the
height of the CG (installing a lift
kit) will increase weight transfer
from the left to the right when
cornering, generally overloading the
right tires and reducing lap times.
Figure 2.8, Estimate of Height of CG
Estimated
Height
of C.G.
+ 5 inches
Ground
Height of Front
This information is not readily
of Crankshaft
available, but can be estimated by
measuring the distance from the
ground to a spot approximately 5
inches above the center of the engine's crankshaft at the front of the engine (typical V-8 camshaft level).
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Chapter 2 Definitions
The Height of C.G. can also be measured by weighing the front and back of the car level, then weighing
it again with one of the car raised. This data can be analyzed by clicking on the Clc button and is
discussed in Section 2.7.4.
Important: The Height of C.G. is used in several calculations, but is VERY difficult to measure exactly,
and NOT really critical to know exactly. For that reason it is recommended that you just estimate as 5
inches higher than the crankshaft height off the ground. If you are still not sure, use 20 inches.
Wheelbase
Is the distance in inches from the center of the front wheels to the center of the rear wheels. Decreasing
the wheelbase usually improves cornering ability because it reduces the moment of inertia of the vehicle.
For example, it is much harder to spin (turn) an 18 foot 2x4 then a 3 foot 4x12, even they both weigh the
same.
Rear Axle Ratio
For most race cars, this is the rear axle ratio or final drive. For chain drive vehicle's (go carts,
motorcycles, etc.) this is the chain ratio. For quick change rear ends, this is the total axle ratio, rear axle
ratio (usually 4.88 or 4.56) times the ratio of the spur gears. Click on the Clc button to obtain a menu to
calculate Rear Axle Ratio based on number of teeth for your particular situation (Section 2.7.5).
Rear Axle Type
This specs tells the program how to estimate the power losses in the rear axle. Generally the more heavy
duty or the more gears in the rear end, the more the power losses.
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Chapter 2 Definitions
Aerodynamics
Type
Click on the down arrow key to pick a general body description, or to “Use Specs Below” where you can
now enter most any combination of specs you want. Then the other aerodynamic specs become enabled
so you can change them. Beginners should pick a general body description Type.
Drag Coefficient
The coefficient of drag (Cd) is an engineering term used to describe how aerodynamic a vehicle's exterior
design is (how easily it "slices" through the wind). A low value for the Cd indicates the car is
aerodynamic and requires little power from the engine to overcome wind resistance. Many automotive
manufacturers now publish the vehicle's Cd in advertising, since an aerodynamic car is a more fuel
efficient car. An aerodynamic car is also a faster car. If the actual Cd of a particular vehicle can not be
found, use Table 2.1 to estimate the Cd for different types of vehicles Use Table 2.2 to estimate how
much Cd and Cl will change from a modification. Table 2.3 shows examples of changing rear spoiler
angle.
Table 2.1: Estimate Drag Coefficient (Cd)
Type of Vehicle
Cd
Motorcycle
Modern Motorcycle (fairings, etc.)
Pickup Truck
Sedan before 1980
Sports Car before 1980
Open Convertible
Modern Aerodynamic Sedan
Modern Aerodynamic Sports Car
“Best Case" vehicle
.70-1.10
.50-.70
.50-.70
.45-.60
.45-.55
.50-.70
.35-.45
.30-.40
.11
Table 2.2: Estimate How Modifications Affect Cd and Cl (lift coefficient)
Modification
Change Cd
Change Cl (lift)
-4 deg Angle of Attack (vs stock) *1
+4deg Angle of Attack (vs stock)
Open Side Windows (vs closed)
Open T-Top & Side Windows
4" Flat Air Dam (width of vehicle) *2
8" Flat Air Dam (width of vehicle)
12" Flat Air Dam (width of vehicle)
1" Flat Spoiler (width of vehicle) *3
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-.04
+.04
+.02
+.08
-.04
.00
+.08
-.03
-100%
+100%
-25%
-50%
-55%
-15%
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2" Flat Spoiler (width of vehicle)
4" Flat Spoiler (width of vehicle)
Blocking half radiator air flow
Circle Track Analyzer
.00
+.08
-.04
Chapter 2 Definitions
-25%
-35%
-35%
Table 2.3 Changing Spoiler Angle on 94 Winston Cup Car
New Spoiler Angle
Change in
20 deg
Cd
Cl
Cd
Cl
Cd
Cl
Cd
Cl
Cd
Cl
30 deg
40 deg
50 deg
60 deg
20
deg
0
0
.011
-.022
.020
-.040
.028
-.053
.034
-.062
Notes concerning Table 2.1, 2.2 and 2.3:
•
•
•
•
•
•
Old Spoiler Angle
30
40
50
deg
deg
deg
-.011
-.020
-.028
.022
.040
.053
0
-.009
-.017
0
.018
.031
.009
0
-.008
-.018
0
.013
.017
.008
0
-.031
-.013
0
.023
.013
.006
-.040
-.022
-.009
60
deg
-.034
.062
-.023
.040
-.013
.022
.006
.009
0
0
Spoiler Angle In Table 2.3
Spoiler Angle In Table 2.2
Change the vehicle's attitude from the production
attitude 4 degrees, where a negative angle of attack is
when the front is lowered and the rear is raised.
For this table, an air dam is defined as a flat plate the
Side View of
full width of the vehicle projecting vertically down
Rear Deck
directly below front bumper (based on typical 1970s or
earlier design). Most modern, production designs
integrate air dams for optimum Cd, therefore adding an
air dam to a modern vehicle will likely show an increase in Cd but perhaps a reduction in Cl.
For this table, a spoiler is defined as a flat plate extending the full width of the vehicle at the top rear
edge of the rear deck (trunk) lid, angled back 20 degrees from vertical. See Figure.
Table 2.2 shows typical effects from modifications. Individual vehicle's can differ considerable.
Advertised Cds are usually the "best case". For a realistic Cd, add .03 to .05 to the advertised Cd for
production vehicles.
Table 2.3 shows effect of changing the spoiler angle on a 94 Winston Cup car. A different body
style and spoiler design would give different results. Changes in the rear spoiler angle affect
downforce on the front and rear of the car differently and can significantly affect handling. To use
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Table 2.3, say you were changing the spoiler angle from 40 to 20 degrees on a car with a .38 Cd and
a -.12 Cl. Forty (40) would be the Old Spoiler angle and 20 would be the New. This would result in
the Drag Coefficient (Cd) decreasing by .020 resulting in .36 and lift coefficient increasing by .040
resulting in a Cl of -.08.
Lift Coefficient
Like Drag Coefficient, the Lift Coefficient is an engineering term which describes how much lift the
car’s shape develops, much like a wing. The higher the Lift Coefficient, the more the lift. However, race
car’s want downforce, not lift, so you want a low lift coefficient A production car will have a Lift
Coefficient in the range from .2 to .3, meaning the car actually unloads the tires somewhat at high speed
(not good). Add some effective spoilers and air dams and this will drop this to close to 0, or that the tires
do not unload at high speed (better). Only when you get into race cars with large wings, spoilers, air
dams close to the ground do you see negative lift coefficients like -.1 or -.2, which actually develop
downforce at high speeds (good). The “ground effects” Indy cars of several years ago actually had lift
coefficients in the range of -1.0 to -2.0, generating tremendous amount of downforce. Check Tables 2.2
and 2.3 to see how Cl (coefficient of lift) is affected by modifications.
To see the amount of downforce or lift being generated from a set of vehicle specs, set the Bank Angle to
0 in the Running Conditions menu. Then the Downforce column in the Test Results will be due only to
aerodynamic downforce, which depends on Lift Coefficient, Frontal Area, vehicle speed and air density.
Technical note: Lift
Coefficient is multiplied by
top area of the car, the
square feet of the car from a
top or plan view. We do not
ask for the top area in the
program, but estimate it as 3
times larger than the Frontal
Area.
Figure 2.9 Frontal Area
Vehicle Height
In v3.6, there is now a Front
and Rear Lift Coefficient.
See Appendix 5.
Frontal Area, sq ft
The frontal area is the area
in square feet the vehicle's
silhouette occupies when
viewed from the front. Use
the formula in Fig 2.10 to
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Track Width
Frontal Area, sq ft = Vehicle Height (in) X Track Width (in)
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estimate frontal area. Frontal areas are in the range of 16 sq ft for a small passenger car to 30 sq ft or
more for a full size pick-up truck. Also see Section 2.7.6 for calculating Frontal Area, sq ft by clicking
on the Clc button.
Transmission
Type
Click on the down arrow of this combo box to pick a general description of the transmission. This choice
only affects power losses. All choices assume a clutch is used between the engine and transmission, not
a torque converter, even if an automatic transmission is used.
Ratio of Trans Gear Used
Is the gear ratio for the single transmission gear used during the race. The Circle Track Analyzer v2.0
assumes the entire race is done in 1 gear. If this is top gear in a “non-overdrive” transmission (3rd for a 3
speed, 4th for a 4 speed, etc), this gear ratio is usually 1. If you are using a Pinto 2.3L SR4 wide ratio
transmission in 3rd gear, this could be 1.66. The program also assumes anything different from 1
produces additional power losses.
Rear Wheel/Tire Specs
Type
Click on this combo box to select general tire type. This choice will have a large effect on overall tire
traction and cornering ability.
Wheels & Tires Wt, lbs
This is the weight of one wheel/tire assembly, which can be obtained by weighing the tire mounted on
the wheel on a weighing (or bathroom) scale.
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Tire Circumference, inches
Left
Right
Circle Track Analyzer
Chapter 2 Definitions
Figure 2.10, Tire Circumference
The circumference of the Left and Right
tires is the distance around the tread as
measured with a tape measure. See Figure
2.10. The difference between the left and
right tires is know as stagger, which is
calculated from your 2 inputs and displayed
here
Circumference
Since Tire Diameter has a Clc button, see
Section 2.7.7 for calculating Tire
Circumference from production tire sizes like P225-60-15.
Tread Width
Is the width of the tire's contact patch on the ground. This number will have a large effect on overall tire
traction, and therefore lap times, especially on short tracks.
Traction Factor
Traction Efficiency describes how well the tires 'hook up' to the road surface. It is affected by road
surface condition, tire conditions (temperature, pressure, compound, etc.) and suspension setup.
Unfortunately, this version of the Circle Track Analyzer is not “smart enough” to know how to use all the
suspension inputs in the Front and Rear Suspension input screens to estimate overall tire traction.
Therefore, use this Traction Factor to “dial in” how well your suspension is working your tires.
Obviously this spec has a critical impact on overall tire traction. Because it depends on so many
variables, it is difficult to estimate. You can click on the Clc button to obtain a general list of estimates.
Most likely you will have to fine tune this estimate based on your vehicle's actual lap times at a particular
track. You can also use the Match Your Lap Times option from the Main Menu to have the program
estimate Traction Factor.
Dirt track conditions can be somewhat simulated by adjusting this Traction Factor down to match your
lap times on dirt tracks.
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2.4 Front Suspension Specs
The Front Suspension menu has 4 major sections, each which will be discussed in this section:
1.
2.
3.
4.
Static Layout Dimensions
Other Misc. Specs
Show Dive & Roll
Suspension Layout Drawing
See Appendix 3, 4 and (especially) 5 for significant new
features added to this Front Suspension screen.
2.4.1 Static Layout Dimensions
Before we define the inputs in this
section, lets take a minute to describe
how you will make these
measurements.
Figure 2.11 Static Layout Dimensions
Section of the Main Screen
Taking Suspension
Measurements
You enter the measurements from your
car's front suspension members into the
Layout Screen. To start, park the car on
a flat, level surface. First we must
decide on what we will call the car’s
centerline. Many people use a distance
half way between the left and right tire
patches. The disadvantage of this method is if you change rim widths or wheel offsets your centerline
can change. This means all your measurements are now off also. Therefore, we usually recommend the
center of the drivetrain, which would be the center of the engine for most car’s front suspensions. This is
a point which will usually will stay in one place. The other advantage of this choice is the rear
suspension’s centerline is now the center of the driveshaft and the pinion gear. This ensures consistency
front and rear for most race cars, and provides an easy reference for most left and right measurements.
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In our Roll Center Calculator program which deals with the front suspension only, we recommend a
distance half way between the frame rails, or the frame mounts on the lower arms. This is usually very
similar to the center of the drivetrain.
On cars without a front engine, rear drive drivetrain layout, use the distance half way between the frame
rails, or the frame mounts on the lower arms. Then be sure to project a line straight back, parallel to the
frame to mark the rear centerline for the rear suspension. You can also use the center of the front tire
patches, being aware of the problem if you change some tire offset specs.
Once you’ve decided on the method, either:
• Drop a plumb bob (pointed weight on a string) down from the center of the crank pulley.
• Use a tape measure to mark a point on the floor which is halfway between the your references.
This will now be your car’s centerline and is 0 in the X (horizontal) direction in the Static Layout
Dimensions section.
When picking a centerline, the most important thing is to be
consistent from front and rear on the same vehicle, and from setup
to setup on the same vehicle. Once you decide on a centerline for
a particular car, you must make all measurements from this same
centerline.
Then with the plumb bob, place the string on the center of a new suspension point to be measured and
drop the bob until it just touches the floor. Measure the distance from the car's centerline to where the
plumb bob points on the floor. This is the "X" distance for that particular suspension point.
You can print a blank worksheet for recording your measurements by clicking on File at the upper left of
the screen (in the Menu Bar), then clicking on Print Blank Worksheet. Be sure you have first selected the
correct Suspension Type (Double A Arm, McPherson Strut, etc) by clicking on Suspension Type in the
Menu Bar to obtain the correct worksheet for your car.
Your choice of Suspension Type will have a large effect on what the Front Suspension screen looks like.
Because Double A Arm is so popular, it will be discusses first. The other suspension types are discussed
only as to what inputs are different than the Double A Arm inputs.
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Figure 2.12, Finding Car Centerline and Measuring Front Suspension Points
(typical X and Height measurement shown for Lower Frame Pivot)
Car Centerline
X
Preferred method is to use
center of engine
crankshaft
Height
Half the distance between
the lower arm mounts can
also be used as centerline
Alternate Car Centerline
Half the Track Width
(the distance between
the center of the tire
patches) can also be
used as the centerline.
Track Width
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For entering dimensions, 2 other options can be important:
Enter X & Ht Readings, Frame & Ball Jnts
Enter X & Ht at 1 End, Arm Len & Angle
If it is easier to measure the lengths or the A Arms and the angle of the A Arms, choose the Arm
Len & Angle option. You still have to measure the X and Height of one end of the arm, but not
both. For the Upper Arm, you will enter the Ball Joint X and Height, and the Length and the
Angle. For the Lower Arm, you will enter the Frame Mount X and Height, and the Length and
the Angle. Changing this option will Enable and Disable the appropriate dimension specs so
you know which values to enter. This option is not available for McPherson Strut suspensions.
See Figure 2.13.
Camber Changes with New Inputs
Camber Does Not Change with New Inputs
For entering a new suspension, it may be better to select the “Camber Does Not Change with
New Inputs” option. This prevents Camber from continually being changed (possibly to very
unusual values) as you enter new measurements. Once you have a new suspension entered,
choosing the “Camber Changes with New Inputs” option works well to see how suspension
adjustments or modifications will change camber. See Figure 2.13.
Enter all the X and Height measurements into the screen. The screen's drawing and calculated values are
updated after each entry. This lets you immediately see if a value you entered looks wrong.
The Roll Center location and Left and
Right Instant Centers are also drawn
in as large dots. Instant Centers are
the imaginary points about which
each side of the suspension tends to
rotate and usually appear on the
opposite side of the suspension. For
example, Right side’s Instant Center
will usually appear on the left side of
the Suspension Layout drawing. The
Roll Center is black on most
computers, and the Instant Centers
match the colors of the Left or Right
suspension drawing. If these locations
are off the screen, they are drawn at
the correct height with an arrow
pointing to their "off screen" location.
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Figure 2.13 Important Options for Entering
Measurements
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Chapter 2 Definitions
Double A Arm Measurements
Upper Ball Joint Location
X is the distance from the car
centerline to the center of the ball
joint on the upper arm on either
the right side or left side, in inches.
Height is the distance from the
ground to this same location. See
pages 27-30 for a definition of
possible centerlines.
Figure 2.14 Measuring Ball Joint Locations
Measure to what you
visualize to be the center
of the ball inside the joint.
Note: If you are using Moog Auto
(part of Cooper Industries) ball
joints, you can call them at 800323-5473 and they will send a
print of the joint to let you more precisely locate the center of the ball.
Upper Frame Pivot Location
X is the distance from the car centerline to the center of the pivot on the frame mount on the upper arm
on either the right side or left side, in inches. Height is the distance from the ground to this same location.
Figure 2.15 Measuring A Arm Length
Top View of A Arm Showing How to Measure Length of A Arm
Draw a line to the
other ball joint.
Length of arm is
w here this line
intersects the
axis of the arm.
Correct
Incorrect
Axis of the arm
is a line joining
front and back
mounting points.
For Strut Suspensions, this line should also
pass through the rear strut mounting point.
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See pages 27-30 for a definition of possible centerlines.
For arms that have angled mounts as many stock arms do or strut mounts, check Figure 2.15 for the most
accurate way to find the arm’s mounting point.
See Appendix 5 for a new feature that makes it easier and more accurate to
determine exactly where the Frame Mounts should be measured.
Lower Ball Joint Location
X is the distance from the car centerline to the center of the ball joint on the lower arm on either the right
side or left side, in inches. Height is the distance from the ground to this same location. See pages 27-30
for a definition of possible centerlines.
Lower Frame Pivot Location
X is the distance from the car centerline to the center of the pivot on the frame mount on the lower arm
on either the right side or left side, in inches. Height is the distance from the ground to this same location.
See pages 27-30 for a definition of possible centerlines.
Upper Spring Pad Location
X is the distance from the car centerline to the center of the upper mounting pad for the spring, in inches.
Height is the distance from the ground to this same location. See pages 27-30 for a definition of possible
centerlines.
Tip: If you are more interested in shock travel than spring travel, enter the top shock mount location.
However, the Wheel Rate calculated from the Spring Rate you enter in the Other Specs section will not
be exactly correct.
Lower Spring Pad Location
X is the distance from the car centerline to the center of the mounting pad for the spring on lower right
arm, in inches. Height is the distance from the ground to this same location. See pages 27-30 for a
definition of possible centerlines.
Tip: If you are more interested in shock travel than spring travel, enter the lower shock mount location.
However, the Wheel Rate calculated from the Spring Rate you enter in the Other Specs section will not
be exactly correct.
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Upper Arm Length
Length of upper right arm from Pivot Center to Ball Joint center as viewed from the front, in inches.
This can be shorter than actual length measured along the arm if arm is swept forward or back. See
Figure 2.15. This spec is only enabled if you have chosen the ‘Enter X & Ht at 1 End, Arm Len &
Angle’ option.
Upper Arm Angle
Angle of the upper left arm as viewed from the front, in degrees. A positive angle means the arm angles
up as the arm goes away from the car centerline, which is typical.
Lower Arm Length
Lower Arm Angle
See Upper Arm Length and Upper Arm Angle explanations above.
McPherson Strut
You can select a McPherson Strut front suspension layout by clicking on Suspension Type at the top of
the Front Suspension screen, then selecting McPherson Strut. The screen will change somewhat. The
Upper Ball Joint and Frame Pivot inputs are changed to Upper and Lower Strut locations. The calculated
Upper Arm Dim. specs have been changed to Strut Dim.
For inputs not shown in this section, see the definitions in the previous Double A Arm section.
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Upper Strut Loc.
X is the distance from the car centerline to the center of the upper mounting point of the strut on either
the right side or left side, in inches. Height is the distance from the ground to this same location. See
pages 27-30 for a definition of possible centerlines.
Figure 2.16 Lower Strut Location
Lower Strut Loc.
X is the distance from the car centerline to the center
of the lower mounting point of the strut on either the
right side or left side, in inches. Height is the distance
from the ground to this same location. The line of
action of the strut must pass through this point.
Therefore if the mount is to the side of the strut’s line
of action, choose the point at the mount’s height, but
the X distance should be at the strut’s centerline or
line of action. See Figure 2.16. See pages 27-30 for a
definition of possible centerlines.
Do Not use mounting holes if
they do not lie on the ‘line of
action’ of the strut.
Use a point which does lie
on the line of action
of the strut.
Straight Axle
You can select a Straight Axle front suspension layout by clicking on Suspension Type at the top of the
Front Suspension screen, then selecting Straight Axle. The screen will change significantly. Only the
Upper and Lower Spring Pads are common with the Double A Arm input specs for Static Layout
Dimensions. The only other inputs concern the Panhard Bar or J bar which locates the front Roll Center.
In the section called Other Specs, calculated specs like Scrub Radius, King Pin Angle and Spindle Angle
are removed.
For inputs not shown in this section (Spring Pad locations), see the definitions in the previous Double A
Arm section.
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Panhard Bar
X is the distance from the car centerline to the center of the Panhard Bar mounting points on either the
right side or left side, in inches. Height is the distance from the ground to this same location. See pages
27-30 for a definition of possible centerlines.
Panhard Bar is Attached to Axle on Which Side:
Select the option which identifies which side (end) of the Panhard bar (or J bar) is attached to the straight
axle. The other end is then attached to the body.
Double A Arm with Torsion Bars
You can select a Double A Arm with Torsion Bars front suspension layout by clicking on Suspension
Type at the top of the Front Suspension screen, then selecting Double A Arm with Torsion Bars. The
screen will change somewhat. The Spring Pad specs are removed from the Static Layout Dimensions. In
the section called Other Specs, calculated specs like Spring Length and Spring Angle are removed, and
the Spring Rate input is changed to T. Bar Rate (torsion bar rate).
Note that Torsion Bar Rate can be calculated by clicking on the Clc button next to
these inputs. See Section 2.7.9. Torsion Bar Rate depends on the bar and the
lower A arm length. Should you calculate a Torsion Bar Rate for a certain lower A
arm length, then change dimensions to simulate a different arm length, the program
will automatically adjust the Torsion Bar rate for what it would be assuming the
same bar is used with the new arm length. However, this may not be what you want
to be simulating. Therefore, it is best that you completely layout all the Static Layout
Dimensions first. Then calculate the Torsion Bar Rate or enter the rate directly.
For inputs not shown in this section, see the definitions in the previous Double A Arm section.
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T Bar Rate
Is the force required to move the ball joint on the lower arm 1 inch, in pounds. The torsion bar is
assumed to be linear, that is if 500 lbs compresses the spring (twists the bar) 1", 1000 lbs will compress
(twists the bar) the spring 2". See Assumptions in Appendix 1 for limits on bar/spring movement. Click
on the Clc button next to these specs to calculate a spring rate (or Torsion Bar Rate from other inputs).
See Section 2.7.9.
2.4.2 Other Specs
Spring Length
Installed or Static length of the spring measured along spring centerline before any Dive or Roll. You
can not enter this value directly. This length is calculated from the X and Height for the Upper and
Lower Spring Pad Locations. This value is useful to check that your X and Height measurements are
entered correctly, as it should closely match your installed spring length.
Spring Angle
Installed angle of spring measured between spring
centerline and vertical, in degrees. You can not enter this
value directly. This angle is calculated from the X and
Height for the Upper and Lower Spring Pad Locations.
This value is useful to check that your X and Height
measurements are entered correctly, as it should closely
match your installed spring angle.
Spring Rate (T. Bar Rate for Torsion
Bar Suspensions)
Is the force required to compress the uninstalled spring 1
inch, in pounds. The spring is assumed to be linear, that
is if 500 lbs compresses the spring 1", 1000 lbs will
compress the spring 2". This is an input which you enter
and effects the Wheel Rate described below. Click on
the Clc button next to these specs to calculate a spring
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Figure 2.17 Other Dimensions &
Specs Section of
Main Screen
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rate (or Torsion Bar Rate from other inputs). See Section 2.7.9. Also see Double A Arm with Torsion
Bars suspension type on previous page, and Assumptions in Appendix 1 for limits on bar/spring
movement.
Wheel Rate
The force required to move wheel center
1 inch up while the chassis does not
move, in pounds. This is a calculated
spec (can not be entered directly) and
depends on the Spring Rate and
suspension geometry.
Scrub Radius
Figure 2.18 Illustration of Camber, King Pin
Axis and Scrub Radius
Camber Angle
Vertical
(negative angle shown here)
Spindle Angle
King Pin Axis
The distance from where the king pin
axis hits the ground and the center of the
tire patch. See Figure 2.18 for King Pin
Axis. This is a calculated spec (can not
be entered directly).
Camber
Scrub Radius
The degrees of tilt of the wheel with respect to the ground as viewed from the front, in degrees. Negative
camber means the top of the wheel tilts in towards the car, which is typical of most race cars. This is an
input which you enter. See Figure 2.18.
Dynamic Camber
The new, Dynamic camber of the wheel caused by Dive and Roll. See Camber above.
Track, in
Track is the distance from the centerline to the center of the tire patch on the ground.
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King Pin Angle
King pin axis is the line intersecting the upper and lower ball joints. The angle is the angle between this
axis and a vertical line. See Figure 2.18. This is a calculated spec (can not be entered directly).
Spindle Angle
Spindle Angle is the angle total of the king pin angle and the camber angle. As long as you are using the
same spindles, the spindle angle must stay the same as you change arm lengths, mounting points or shim
the arms in and out. Spindle Angle is not displayed unless you have selected the Front Suspension
option of “Show Spindle Angle”. See Figure 2.18
Roll Bar Rate
Is the force required to move one arm of the roll bar 1 inch, in pounds, while the other arm does not
move. The bar is assumed to be linear, that is if 500 lbs moves the arm 1", 1000 lbs will move the arm
2". This is an input which you enter and effects the vehicle’s roll stiffness. Click on the Clc button next
to this spec to calculate a Roll Bar Rate. See Section 2.7.10.
Roll Bar Length
Is the length of the roll bar in inches. This length tells the program where the bar attaches to the lower
arms, and therefore lets the program determine the motion ratio of the bar
2.4.3 Show Dive & Roll
As shown in Figure 2.19, you must first select the Yes option in this section before any of these inputs or
command buttons become enabled.
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Figure 2.19 Roll & Dive Options
Choose the Yes option to enable Dive and Roll
Type in Dive and/or Roll here,
Or click on Arrow buttons to
increment automatically
Click here to draw layout big
and show spring compression
Dive
The amount the car's front end drops compared to its static (standing still) height. To simulate the front
end rising, enter a negative (-) number.
Roll
The amount the car's front end rolls (leans) due to cornering forces, compared to its static (standing still)
angle. A positive (+) angle means the car is leaning to the Right, typical of Left turns. Use a negative (-)
number to lean Left (Right turns).
Draw ‘Big’
This command button lets you select a screen mode where the Suspension Layout is drawn about twice
its normal size. In this mode you can see things in more detail. The Draw ‘Big’ mode also displays
Spring Deflection, which is not displayed in the Normal Sized screen.
Spring Deflection
The change in the length of the spring due to Dive or Roll. Negative (-) means spring compression from
diving, positive (+) means elongation from rising. Since shocks generally are mounted close to the
spring locations, shock travel is very similar to Spring Deflection.
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2.4.4 Suspension Layout
The features of the Suspension Layout drawing are discussed in Figure 2.20 below.
Figure 2.20 Major Features of the Suspension Layout Screen
Camber Gain and the motion on which it is based is given in this line.
Right Instant Center drawn in blue just like the right side suspension.
The arrow drawn in this Figure (not on the computer screen) shows how
it has moved from its static location (gray dot with blue outline).
Left Instant Center drawn in red just like the left side suspension. The
arrow drawn in this Figure (not on the computer screen) shows how it
has moved from its static location (gray dot with red outline). The red
arrow pointing off the screen shows its actual location is off the screen.
Roll Center drawn in black. The arrow drawn in this Figure
(not on the computer screen) shows how it has moved from
its static location (gray dot with black outline).
Dynamic Roll Center
location (due to Dive and
Roll)is shown in black.
Static Roll Center location is shown in black, unless the
car is in Dive and/or Roll. Then it is shown in gray (as
shown here) for comparison to the Dynamic Roll Center.
Letters A-L relate to dimensions listed in Static Layout Dimensions section. See page 27.
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Tips for understanding Roll Center and Camber Gain discussed
in Figure 2.20 are listed at the end of Appendix 2.
Menu Options
In the Menu Bar at the top of the Front Suspension screen, there are 7 main menu commands:
1. Back
2. File
3. Options
4. Suspension Type
5. Shim
6. Comments
7. Help
These are discussed in this section.
Figure 2.21 Menu Bar Options Available
File
Figure 2.22 File Options
Click on File to present several standard Windows File
options:
New Front Suspension blanks out all the current spec
inputs, calculated values, comments and changes the current
Front Suspension file name to Untitled.
Open Example Front Suspension presents the
Circle Track Analyzer’s File Open screen, where you can open
an Example Front Suspension file which was provided by
Performance Trends. These examples include comments and all measurements for the particular Front
Suspension Type. These are provided to let you see typical measurements for different types of Front
Suspensions, and are saved in the XFRONT folder (directory).
Open Saved Front Suspension is much like Open Example Front Suspension command above
except: 1) You are presented Front Suspension Files that you have saved. (See the Save commands
below.) These are saved by default to the FRONT folder (directory). 2) You can click on the File Open
screen’s Advanced button and be presented with the standard Windows File Open dialog box. From
there you can open a Front Suspension file or even a Roll Center Calculator (another Performance Trends
program) file which you have saved somewhere else. You can select different directories or disk drives
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for files. You can choose most any file, but if the program senses the file is not a Front Suspension or
Roll Center Calculator file, you will be given notice and the file will not be opened.
Save saves the current Front Suspension specs to the current file name. This is a shortcut to update the
current file with the current specs and measurements.
Save As presents the standard Circle Track Analyzer Save screen, where you can save the file to most
any name of your choosing. Save As is how you change the name of a Front Suspension file. At this
screen you can also click on the Advanced button which presents a standard Windows File Open dialog
box (not shown in Beginner Level). Then you can save a Front Suspension file to a name of your
choosing. Certain names are not acceptable, including:
• Names with more than 3 characters to the right or 8 characters to the left of a period (.) .
• Names over 11 characters long (12 characters if one is a period).
• Names which include the characters:
/ \ [ ] : | < > + = ; , * ? or spaces
You can also select different directories or disk drives for saving files.
Print prints the Front Suspension Screen.
Print Blank Worksheet prints the Front Suspension screen with blank boxes for all inputs.
Windows Print Setup opens the standard Windows menu for selecting the printer, page orientation,
etc.
Options
Click on Options for the list shown in Figure 2.23.
Enter X & Ht Readings, Frame & Ball Jnts
Enter X & Ht at 1 End, Arm Len & Angle
If it is easier to measure the lengths or the A Arms and the angle of the A Arms, choose the Arm Len &
Angle option. You still have to measure the X and Height of one end of the arm, but not both. For the
Upper Arm, you will enter the Ball Joint X and Height, and the Length and the Angle. For the Lower
Arm, you will enter the Frame Mount X and Height, and the Length and the Angle. Changing this option
will Enable and Disable the appropriate dimension specs so you know which values to enter. This ‘Len
& Angle’ option is not available for McPhErson Strut suspensions. For more details, see the Example
4.3.
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Draw Extension Lines
Don’t Draw Extension Lines
Chapter 2 Definitions
Figure 2.23 Main Screen Options Menu
Lets you choose if imaginary extension lines
should be drawn in the Suspension Layout.
These extension lines help show how the
Instant Centers and Roll Center are arrived at.
Background Car Layout Color Light Gray
Background Car Layout Color Dark Gray
Lets you select the color for the background
car and suspension drawing in the Layout
screen. The Background Car shows the static
position of the suspension and car before any Dive and/or Roll.
Camber Changes with New Inputs
Camber Does Not Change with New Inputs
For entering a new suspension, it may be
better to select the “Camber Does Not
Change with New Inputs” option. This
prevents Camber from continually being
changed (possibly to very unusual
values) as you enter new measurements.
Once you have a new suspension
entered, choosing the “Camber Changes
with New Inputs” option works well to
see how suspension adjustments or
modifications will change tire camber.
Figure 2.24 Camber Gain Specs Menu
Camber Gain Definition Specs
Click on this option and you get the
menu of Figure 2.24. This menu lets you
change the amount of body movement
the program uses to determine Camber
Gain.
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First you select the Type of Calc, which means either to use the program's standard definition of 1" of
Dive with No roll, or to Use Specs Below (in this menu).
If you select to Use Specs Below, the Body Dive, inches and Body Roll, degrees specs become enabled
so you can enter or change them. If you click on the OK/Exit button while Use Specs Below is selected,
the Camber Gain at the Main Screen will now be based on these custom specs. This definition is always
displayed in the Suspension Layout screen as shown in Figure 2.20.
Click on Cancel to close this menu and return to the original specs used for calculating Camber Gain.
Tips on Camber Gain are listed at the end of Appendix 2.
Show Spindle Angle
Don’t Show Spindle Angle
Lets you select whether Spindle Angle is displayed. Some users may find Spindle Angle confusing, so
the program comes from the factory with these specs not displayed.
Figure 2.25 Suspension Types
Suspension Type
Click on Suspension Type to choose the type
of Front Suspension layout. As you change
Suspension Type, various options will be
enabled or disabled. For example, the Shim
option for inputting the Length and Angle of
the Strut are only available for Double A Arm
suspensions. Also realize that if you switch
Suspension Types with a current set of
suspension dimensions, the drawing will look
very unusual.
Figure 2.26 shows major differences for the McPherson Strut Suspension Type.
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Figure 2.26 McPherson Strut Suspension Type
Camber Gain Definition is
always shown here
Struts replace the arms
drawn for the Double A
Arm suspension type.
Strut dimensions replace
the Upper Arm
dimensions here also.
The Shim option or
inputing the Length and
Angle of the Strut are not
available for this
suspension type.
Shim
Click on Shim when this option is enabled, and then select from the choices of shimming the left or right
arm You are then presented with the menu shown in Figure 2.27.
This menu lets you move the Frame Pivot point of the upper A arm in or out, as is usually done by
adding or removing shims. The software keeps the length of the arm constant and calculates where the
Ball Joint end will be after the adjustment.
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First, select whether you want to Add or
Remove shims from the first Combo box.
Then select whether you want to use
standard sixteenth (1/16) and eighth (1/8)
inch shims, or to enter some other
'Custom' shim adjustment. After your
selection, the lower inputs will become
enabled as appropriate. Selecting 'No
Shims' disables the lower inputs.
Circle Track Analyzer
Chapter 2 Definitions
Figure 2.27 Shimming Menu for Right Side
An estimate of the new Camber is given at
the top for the shim adjustment currently
entered, with the Current Camber also
given for comparison. (If you have Not
selected the option at the Main Screen that
Camber should be adjusted with changing
dimensions, you will be asked if you want
Camber to be adjusted before it is.)
The entries and suspension layout on the
Main Screen are not updated until you
click on 'Use Calc Value'.
Important: This menu assumes that Adding shims moves the Frame Pivot farther
out from the car (reducing negative camber or increasing positive camber). Some
chassis (for example: the left side on some Lefthander Chassis) work the opposite,
adding shims moves the pivot inward. If your chassis is like this, select 'Remove
Shims' if you are actually adding shims or 'Add Shims' if you are actually removing
shims.
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Comments
Click on Comments for the Comment Editing screen shown in Figure 2.28. Comments are printed with
your other specs when you request a print of the Front Suspension screen (at least the first 300 characters
or so), when you print Vehicle Specs with the Calculated Results, and are saved with a Front Suspension
file and with the complete Vehicle File. Comments are a good way to keep track of what each saved file
is.
Figure 2.28 Comments Editing Screen
Click here and start typing to change a
comment.
Click here to
enable all
comments
to be
editted. All
comments
will now be
printed in
black
instead of
gray.
Click here to abandon any changes made to
the comments.
Click here to keep your changes.
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2.5 Rear Suspension Specs
The Rear Suspension menu is similar to the Front Suspension screen described in Section 2.4, but is
simpler. It describes the Rear Suspension layout and measurements. The top choice of Rear Suspension
Type has a large effect on how this screen looks and what measurements can be entered.
Check Appendix 4 for new Rear Suspension types, like Angled 4 Link.
Figure 2.29 Rear Suspension Screen for Suspension Type: Truck Arms
Menu Commands
Type is a critical spec which dictates what this screen looks like and
what inputs are used.
Name of current Rear Suspension File
Layout screen shows how program is using your measurements.
This is handy way to spot errors in inputs. Screen also shows
calculated results like Wheel Rates and Roll Center Location.
Help box gives brief description of spec you have clicked on.
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Taking Suspension Measurements
You make measurements and enter them into this screen much as you do for the Front Suspension. Start
by parking the car on a flat, level surface. First we must decide on what we will call the car’s centerline.
Many people use a distance half way between the left and right tire patches. The disadvantage of this
method is if you change rim widths or wheel offsets your centerline can change. This means all your
measurements are now off also. Therefore, we usually recommend the center of the drivetrain, which
would be the center of the engine for most car’s front suspensions. This is a point which will usually will
stay in one place. The other advantage of this choice is the front suspension’s centerline is now the
center of the engine. This ensures consistency front and rear for most race cars, and provides an easy
reference for most left and right measurements.
On cars without a front engine, rear drive drivetrain layout, use the distance half way between the frame
rails, or the frame mounts on the lower arms. Then be sure to project a line straight back, parallel to the
frame to mark the rear centerline for the rear suspension. You can also use the center of the front tire
patches, being aware of the problem if you change some tire offset specs.
Once you’ve decided on the method, either:
• Drop a plumb bob (pointed weight on a string) down from the center of the driveshaft or pinion gear.
• Use a tape measure to mark a point on the floor which is halfway between the your references.
This will now be your car’s centerline. All measurements asking for a distance from something to
Centerline is a measurement from this centerline our to either the left or the right. For example, Tire to
Centerline is the distance from the center of the tire patch on the ground to the car’s centerline.
When picking a centerline, the most important thing is to be
consistent from front and rear on the same vehicle, from setup to
setup on the same vehicle, and from vehicle to vehicle. Once you
decide on a centerline for a particular car, you must make all
measurements from this same centerline.
With the plumb bob, place the string on the center of a new suspension point to be measured and drop the
bob until it just touches the floor. Measure the distance from the car's centerline to where the plumb bob
points on the floor. This is the distance to Centerline for that particular suspension point.
You can print a blank worksheet for recording your measurements by clicking on File at the upper left of
the screen (in the Menu Bar), then clicking on Print Blank Worksheet. Be sure you have first selected the
correct suspension Type (Trailing Arms, Leaf Springs, etc) by clicking on Type at the top of the inputs to
obtain the correct worksheet for your car.
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Trailing Arm / Truck Arm Measurements
Figure 2.30 Trailing Arm Rear Suspension Layout
Axle to Front Pivot
Spring to Centerline
Spring to Axle (positive
direction, ahead of axle)
Spring to Axle (negative
direction, behind axle)
Tire to Centerline
Pnhd Bar to Centerline
Calculated Wheel Rates
Spring Angle
Drawn Roll Center (black
dot)
Panhard Bar Heights
Roll Center Location
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Type
Click on down arrow button to pick a type of Rear Suspension Layout. Your choice here will have a
large effect on how this screen looks and what measurements can be entered. Truck Arms are nearly
identical to Trailing Arms except they are usually longer, and they angle in toward the center of the car,
usually pointing toward the transmission.
Spring Rate
Force required to compress the uninstalled spring 1 inch, in pounds. The spring is assumed linear, that if
500 lbs compress the spring 1", 1000 lbs will compress the spring 2". Click on the Clc button to
calculate spring rate for either a coil spring, leaf spring or torsion bar. See Section 2.7.9. See Appendix
1 for limits of spring movement.
Tire to Centerline, in
Distance from car centerline to center of tire patch on the ground, inches. For ease of consistent
measurements for front and rear, use the center of the drivetrain (engine, trans, rear axle) as the car's
centerline.
Spring to Centerline, in
Distance from car centerline to center of the spring mount pad, in inches. For ease of consistent
measurements for front and rear, use the center of the drivetrain (engine, trans, rear axle) as the car's
centerline.
Spring Angle, deg
Installed angle of spring measured between spring centerline and vertical, in degrees. Positive angles tip
in toward car centerline at top.
Spring to Axle, in
Distance from axle centerline to center of the spring mount pad, in inches. If the spring is behind the
axle, enter a negative (-) number.
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Front Pivot to Axle, in
Distance from axle centerline to attachment point of the trailing arm on the body, in inches.
Pnhd Bar to Centerline, in
Distance from car centerline to the Pan Hard bar (or J bar) pivots on the frame, in inches. For ease of
consistent measurements for front and rear, use the center of the drivetrain (engine, trans, rear axle) as the
car's centerline.
Panhard Bar Heights, in
Distance from ground to the Pan Hard bar (or J bar) pivots on the frame, in inches.
Leaf Springs
If you select Leaf Springs, the Spring Rates and Tire to Centerline are the same as described in the
Trailing Arm / Truck Arm section, except you would enter the spring rate calculated for a leaf spring.
With Leaf Springs, only measurements from one side are used because the program assumes leaf spring
suspensions are symmetrically laid out (same measurements left and right). However, you can still
specify a different spring rate and tire track left and right.
Spring to Centerline
Distance from the center of the leaf spring to the centerline of the car in inches.
Spring Front to Axle
Distance from axle centerline forward to the leaf spring front mount on the frame, in inches.
Spring Front Height
Distance from the leaf spring’s front mount down to the ground, in inches.
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Spring Rear to Axle
Distance from axle centerline back to the leaf spring’s shackles rear mount on the frame, in inches.
Figure 2.31 Leaf Spring Measurements
Spring to Centerline
Spring Front to Axle
Spring Rear to Axle
Roll Center
Spring Rear Height
(measure to where
shackles attach to frame)
Spring Front Height
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Spring Rear Height
Distance from the leaf spring’s shackles rear mount on the frame, in inches.
Torsion Bars
If you select Trailing Arm/Torsion Bars/Panhard Bar for a Suspension Type, the layout is very similar to
the Trailing Arm / Truck Arm shown in Figure 2.30. The only difference is the round coil spring is
drawn as a torsion bar with an arm the rests on the axle. The input Spring Rate is switched to T.Bar
Rates, lb/in.
T.Bar Rates, lb/in
The spring rate of the Torsion Bar with its lever arm. This can be calculated by clicking on the Clc
button, as described in Section 2.7.9. Note that if the effective length of the lever arm changes, the
Torsion Bar rate also changes. This includes just moving the torsion bar closer or farther from the axle.
T.Bar Arm to Centerline
The distance from the center of where the Torsion Bar’s arm rests on the axle housing to the car’s
centerline, in inches. See Figure 2.32.
Jacob’s Ladder
If you select Trailing Arm/Torsion Bars/Jacobs Ladder for a Suspension Type, the layout is similar to the
Trailing Arm / Truck Arm shown in Figure 2.30. The 3 major differences are:
1. The round coil spring is drawn as a torsion bar with an arm the rests on the axle.
2. The input Spring Rate is switched to T.Bar Rates, lb/in.
3. The Panhard Bar (or J bar) specs are replaced by the Jacob’s Ladder inputs shown in Figure 2.32.
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Figure 2.32 Torsion Bar with Jacob’s Ladder Suspension Layout
T. Bar Arm to Centerline
Roll Center Location
B
E
“To C/L” measurement for point
D. Other measurements done is
a similar fashion. If a point lies
to the left of the centerline, enter
a negative number.
A
D
“Ht” measurement for point D.
Other measurements done is a
similar fashion.
Jacobs Ladder Layout
The 2 mounting points on the 2 links of the Jacobs Ladder are identified by the letters A, B, D and E as
shown in Figure 2.32. Enter the measurements for each mounting point as described below.
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To C/L
Distance from car centerline going Right to the mounting point of Upper Link or Lower Link of the
Jacob’s Ladder mounting points, in inches. Enter a negative (-) number if this point is to the left of the
car’s centerline. For ease of consistent measurements for front and rear, use the center of the drivetrain
(engine, trans, rear axle) as the car's centerline.
Ht
Distance from the ground to the mounting point of Upper Link or Lower Link of the Jacob’s Ladder
mounting points, in inches. Enter a negative (-) number if this point is to the left of the car’s centerline.
For ease of consistent measurements for front and rear, use the center of the drivetrain (engine, trans, rear
axle) as the car's centerline.
Menu Options
Figure 2.33 Menu Bar Options Available
In the Menu Bar at the top of the
Rear Suspension screen, there are 4
main menu commands:
1. Back
2. File
3. Comments
4. Help
These are discussed in this section.
Figure 2.34 File Options
File
Click on File to present several standard Windows File
options:
New Rear Suspension blanks out all the current spec
inputs, calculated values, comments and changes the current
Rear Suspension file name to Untitled.
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Open Example Rear Suspension presents the Circle Track Analyzer’s File Open screen, where
you can open an Example Rear Suspension file which was provided by Performance Trends. These
examples include comments and all measurements for the particular Rear Suspension Type. These are
provided to let you see typical measurements for different types of Rear Suspensions, and are saved in
the XREAR folder (directory).
Open Saved Rear Suspension is much like Open Example Rear Suspension command above
except: 1) You are presented Rear Suspension Files that you have saved. (See the Save commands
below.) These are saved by default to the REAR folder (directory). 2) You can click on the File Open
screen’s Advanced button and be presented with the standard Windows File Open dialog box. From
there you can open a Rear Suspension file which you have saved somewhere else. You can select
different directories or disk drives for files. You can choose most any file, but if the program senses the
file is not a Rear Suspension file, you will be given notice and the file will not be opened.
Save saves the current Rear Suspension specs to the current file name. This is a shortcut to update the
current file with the current specs and measurements.
Save As presents the standard Circle Track Analyzer Save screen, where you can save the file to most
any name of your choosing. Save As is how you change the name of a Rear Suspension file. At this
screen you can also click on the Advanced button which presents a standard Windows File Open dialog
box (not shown in Beginner Level). Then you can save a Rear Suspension file to a name of your
choosing. Certain names are not acceptable, including:
• Names with more than 3 characters to the right or 8 characters to the left of a period (.) .
• Names over 11 characters long (12 characters if one is a period).
• Names which include the characters:
/ \ [ ] : | < > + = ; , * ? or spaces
You can also select different directories or disk drives for saving files.
Print prints the Rear Suspension Screen.
Print Blank Worksheet prints the Rear Suspension screen with blank boxes for all inputs.
Windows Print Setup opens the standard Windows menu for selecting the printer, page orientation,
etc.
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Comments
Click on Comments for the Comment Editing screen shown in Figure 2.28 for the Front Suspension
Comments. Comments are printed with your other specs when you request a print of the Rear
Suspension screen (at least the first 300 characters or so), when you print Vehicle Specs with the
Calculated Results, and are saved with a Front Suspension file and with the complete Vehicle File.
Comments are a good way to keep track of what each saved file is.
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2.6 Calculate Performance
2.6.1 Running Conditions
At the Main Menu, you can calculate lap time performance by:
1. Clicking on Calculate Performance to open the Running Conditions menu, then clicking on
Calculate Performance.
2. Clicking on the Calc Lap Times button at the top of the Main Menu.
Figure 2.35 Running Conditions Menu
This combo box lets you select the combination of weather
instruments you will use, including an altimeter.
Track Specs with
general layout showing
how track looks
Click on Type and you can pick a
typical or specific track, or choose Use
Specs Below to design your own
track.
Driver Specs
describe how
aggressively
you drive, or
how close
you take the
car to the
limits of the
tire’s traction.
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If you click on Calculate Performance, you will first be presented with a menu of conditions which
describe how you will "run" this vehicle. These conditions include:
• Weather and wind conditions.
• How often to report results in the output, for example every 0.5 seconds.
• Track specs like length, banking, etc.
• How you drive your vehicle with respect to accelerating and braking.
Track Weather
The weather conditions affect both the air's oxygen density which affects engine power, and the air's total
density which affects aerodynamic drag. Many racers use their own personal “weather stations”. In
these cases, be sure you read the Notes on Weather Conditions at the end of this section., page 62.
Method of Recording Weather Data
Click on the down arrow button of this combo box to be presented with this list of options:
• Radio/TV Report with Rel Hum
• Radio/TV Report with Dew Pt
• Uncorr. Baro with Rel Hum
• Uncorr. Baro with Dew Pt
• Pick a typical “day” . This is an easy method to use reasonable weather conditions when you
are not particularly interested in how changes weather conditions will affect performance.
If you change the Method, the 4 inputs specs in the Weather section are changed or enabled/disabled as
necessary to represent the new Method. In addition, all the input specs are adjusted to what they would
be with the new Method. For example, Corr. Barometer of 29.3” at an elevation of 1200 feet is
converted to 28.03” Obs Barometer with Elevation disabled. (Elevation is not important when you are
using an uncorrected or observed barometer, as this type of barometer shows the actual air pressure at the
track.)
If you change from “Uncorr Baro” to Radio/TV Report with a “Corr. Baro”, the program will ask for an
Elevation for the track, since this is needed to make the Barometer Correction. All these different inputs
are explained below.
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Barometric Pressure
Corr. Barometer, ''Hg
This input is used for either “Radio/TV Report with Rel Hum” or “Radio/TV Report with Dew Pt”. It is
the Corrected Barometric Pressure in inches of Mercury you will hear from most any TV or radio
weather report. This spec is disabled if you picked a Typical day, but will display the barometer being
used.
Obs. Barometer, ''Hg
This input is used for either “Uncorr. Baro with Rel Hum” or “Uncorr. Baro with Dew Pt”. It is the
actual or observed Barometric Pressure in inches of Mercury at the track. These barometers measure the
actual air pressure at the track, and will read approximately .1 inches of mercury less than the barometric
pressure you will hear from a TV or radio weather report for each 100 feet of elevation. This spec is
disabled if you picked a Typical day, but will display the barometer being used.
Air Temperature
Air Temperature deg F
Air temperature in degrees F of the air at the track. This spec is used for all Methods of Recording
Weather Data. This spec is disabled if you picked a Typical day, but will display the temperature being
used.
Humidity
Relative Humidity, %
Describes the air’s humidity level in percent of humidity the air could hold at its present temperature.
Relative Humidity can be calculated from either wet and dry bulb temperatures, or from dew point and
air temperature readings by clicking on the Clc button. See Section 2.7.11 and 2.7.12.
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Dew Point, deg F
The dew point in degrees F of the air at the track, which describes the air's humidity level. The Dew
Point, deg F must be less than the Air Temperature. Dew Point can be calculated from either wet and dry
bulb temperatures, or from relative humidity and air temperature readings by clicking on the Clc button.
See Section 2.7.11 and 2.7.12.
Dew Point is a less confusing way of describing the air's moisture level than relative humidity. Relative
humidity readings are only meaningful if the air temperature when the reading was made is also known.
However, the air's dew point remains constant even when the air temperature changes. For example, 40
degree air with a 80 % relative humidity has only a 10% relative humidity when the same air is heated to
100 degrees. However, the dew point remains at 36 degrees for both air temperatures.
Elevation
Elevation, ft
The elevation of the track above sea level in feet. This spec is only used if you are using a Corrected
Barometer, like from a TV or radio station weather report. If the elevation is below sea level, enter a
negative (-) feet for this reading. This spec is disabled if you picked a Typical day, but will display the
elevation being used.
Notes on Weather Readings and Weather Stations
Many racers will use “weather stations”, a collection of temperature, humidity and barometric pressure
measuring devices. When using these instruments, here are some things to keep in mind:
• Unless you are very close to sea level, an actual (observed or uncorrected) barometer will usually
read less than a TV or radio weather report barometer. For elevations less than 5000 feet, an
uncorrected barometer should read approximately 0.1 “ Mercury less for each 100 feet of
elevation above sea level. For example, if your barometer instrument is at 850 feet elevation and
the closest weather station reports 30.46” barometric pressure, your barometer should read
approximately .85” (850/100 x .1) less, or 30.46-.85= 29.61. It is useful to keep records of
information like this (what your actual barometer reads versus what this simple calculation says it
should approximately read) to see if the comparison is constantly jumping around. If you always
make the check at the same place (same elevation) like your home or shop, and the difference is
varying high by .1”, than low by .2”, etc., you may want to have the barometer or altimeter
checked out.
• If you find that you are making many adjustments to your weather station, you are probably doing
something wrong. A barometer which reads low, but consistently reads low is better for
predicting performance trends, than one you are trying to keep accurate by constantly adjusting. it.
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Unless you are racing in very different air, you are probably better off not changing jets. Unless
you know if you were on the rich side or lean side to start with, you may actually be making things
worse. Also, constant carb adjustments are just one more thing to go wrong and cause
inconsistency.
Reports/Graphs
Reports Results Every...
Click on this combo box to select how often to report results. The smaller the time increment you
choose, the more detailed the graphs, tabular results and Suspension Analysis. However, the tabular
results are much longer, up to 100 rows of results, which makes for long printouts.
Track Specs
Figure 2.36 Track Specs
Type
Click on arrow to select how you want to
describe the race track. The first choice
of 'Use Specs Below' enables all track
specs so you can describe most any track,
or you can pick from the preloaded
Typical or specific tracks in the list.
I
Track Length
follow ing
line driven
by the car.
Infield Width
Track Length, ft
The distance around the track following the 'line' the car will drive, in feet.
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Infield Width, ft
The distance across the infield in feet. This tells the program how tight the turns are.
Bank Angle, deg
Is the banking of the track in the corners in degrees, for the line the car drives. If the banking is
progressive (steeper at the top), enter the banking for where the car drives (low banking if the car stays
low).
Driver
Type
Click on arrow to select how you want to describe the driver. The first choice of 'Use Specs Below'
enables both Driver specs so you can enter both individually, or you can pick from the preloaded Typical
examples in the list.
Accel. Aggressiveness
Click on arrow to select how quickly the driver gets on the accelerator out of the turn. The more
aggressive the rating, the closer the driver keeps the tires to the limits of the 'Friction Circle' (on the edge
of 'breaking loose').
Brake Aggressiveness
Click on arrow to select how deep the driver goes into the turn before braking, then how hard they brake.
The more aggressive the rating, the closer the driver keeps the tires to the limits of the 'Friction Circle'
(on the edge of 'breaking loose').
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2.6.2 Calculate Performance Test Results
Figure 2.37 Calculated Results
Improvement Summary
Click here to show History
Summary of Important Notes
Test History (not always shown)
Commands buttons for analyzing results
Tabular Results
The Circle Track Analyzer's calculated output is shown in Figure 2.37 above. This screen shows the
track performance for the current vehicle. From this screen you can:
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•
•
•
•
•
•
•
•
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Chapter 2 Definitions
Graph or plot the results versus time by clicking on the "Graph" menu command or the "Graph"
icon. Additional help is available from the Graph Screen.
Print the results on a printer by clicking on the "Print" menu command or the "Printer" icon.
Under the "Print" menu command, several other options open up for various types of report and
printer options.
View the program's Notes about these results by clicking on the "Notes" button. Notes are
useful for pointing out possible problems with the combination of specs you have selected. A
brief summary of the notes is given in the "Notes Summary" frame.
Display a history of the last 25 runs you have made by clicking on the "History" menu command.
Analyze the suspension by clicking on Analyzer Suspension. This displays a screen showing
several aspects of suspension motion and handling analysis. Several report options are also
available at this screen, some to give 'starting point' recommendations for springs, roll bar rates,
stagger, etc. These options are a powerful part of the Circle Track Analyzer's analysis.
Analyze the results in an Analysis Report by clicking on the "Analyze Perf" menu command. The
analysis report gives tips on what to look for in the results to improve performance, or warning
of unsafe conditions to be aware of.
Return to the Main Menu by clicking on the "Back" menu command.
You can obtain definitions for most results by clicking on that area of the screen with the mouse.
For example, click on the column with MPH results, and a definition of MPH appears with a page
# in the manual for more info. This also works for the History report in the lower area of the
screen, if it is currently being displayed.
Improvement Summary
The Improvement Summary section compares the final results of the current run with those of the
previous run. This saves you from writing down Lap Times and MPHs to see how much effect a given
modification has on performance.
Lap Time
Is the time for the car to travel around the track. The results only show what happened from start of Turn
#2, through the straight away, then through Turn #3. The assumptions is that the other half of the track is
exactly the same and those results are not calculated or shown.
MPH (Final Velocity in Miles per Hour)
Is the vehicle's average velocity around the track in miles per hour.
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Improvement
Improvement is simply the difference between the Current Run and the Last Run for which performance
was calculated.
If the improvement is a positive value:
• The Current Run’s Lap Time was quicker (shorter) than the Last Run’s
• The Current Run’s MPH was faster (greater) than the Last Run's
Tabular Results
The tabular results gives important vehicle and engine information at significant points during the run:
• At the start of Turn #2.
• At every time interval you have requested in the Running Conditions menu as Report Results
Every... spec in the Reports/Graphs section.
• At the beginning of braking.
• At the end of Turn #3.
Occasionally, two of these conditions may occur very close together. For example 8.0 seconds may
occur a couple hundredths of a second before the start of braking. In these cases, you may only get one
reading, either the 8.0 second point or the start of braking.
The following section defines each data column:
Sec
Shows the elapsed time since the start of Turn #2.
The resolution of the time column can be increased to thousandths of a second by selecting .001 second
increments in the Preferences menu
MPH
Is the vehicle's velocity in MPH.
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Feet
Is the distance the vehicle has traveled during the run, measured in feet.
Accel Gs
Is the vehicle's acceleration in Gs (1 G being 22 MPH/second). If the tires are likely to loose traction,
being overpowered by the available torque, the G value is followed by an S, and you should see
Throttle% being less than 100%.
Engine RPM
Is the engine RPM.
% Thrt
Is the percent of the engine’s HP being allowed to be delivered to the clutch. This will be reduced from
100% to prevent tire spin it tire spin is likely due to lack of tire traction.
Turn #
Since the program calculates only half the track (assuming the other half is exactly the same), two values
are displayed. When a dash (-) is displayed, the car is on the straight away.
Curvature
The radius of curvature for the line the program assumes the driver is driving, in feet. The smaller the
number, the sharper the turn at that point.
Downforce
Downforce is the force in pounds pressing the tires onto the track due to banking and aerodynamics,
above normal vehicle weight. If this value is less than 0, it will be shown as a negative (-) value.
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Corner Gs
Corner Gs is the cornering force which is throwing the car and the driver to the outside of the turn,
measured in Gs.
Figure 2.38 Diagram of Downforce and Corner Gs
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2.7 Calculation Menus:
The following section explains the user input for specs listed with Clc buttons (and the “Calculate”
power curve menu option in the Engine Specs menu). These specs are ones where you can simply enter a
value, or click on the Clc button and the program will present a menu of inputs which will calculate that
particular parameter. These menus are like
computer “scratch pads” for calculating specs like
Figure 2.39 Typical Calculation Menu
Final Drive Ratio, Tire Circumference, etc. from
other inputs.
Notes:
The starting values in each calculation menu are
usually blanked out when the menu is opened. If
there is other information in the program to
estimate what one of your input values will be, it
may be loaded. As shown in Figure 2.39, the 4
corner weights are already available based on the
Vehicle Weight and Weight %s in the Vehicle
Specs menu, and these values are loaded into the
Calculation Menu. You are free to change them to
any other value.
Once enough specs have been entered, the
calculated value(s) at the top of the menu will be
displayed. This calculated value(s) will now be
updated each time you change a spec. If you want
to use this calculated value, click on Use Calc
Value. If the calculated value is within expected
limits, it will be loaded into the original menu. If
you click on Cancel, you will be returned to the
original menu with the original value unchanged.
If you click on Help, you will be given a general explanation of calculation menus, and a page # in this
section for more info about the particular menu you are using.
The input values or calculated values in any calculation menu have NO affect on calculated performance
unless you load the Calculated value into the original menu. If you already know a spec in the form
required by the program, then you have no need to use the calculation menu. For example, if you
know the Relative Humidity is 88%, then you have no need to use a calculation menu to calculate
Relative Humidity from , say, wet and dry bulb temperatures.
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Example
Assume you want to calculate a power curve for your car, but you know very little about the engine.
You could click on the Calculate menu item in the Engine Specs menu. You will be presented with the
menu shown in Figure 2.40.
Engine Cubic Inches is already available from the Engine Specs menu, and this value is already loaded
into the Calculation Menu. Since the Cubic Inches of 355 is accurate for your engine, you leave it “as
is”.
Note that most inputs are disabled except Calc
Based On and Engine Cubic Inches. Select the
Calc Based On choice from this Combo box.
Since you may not know what Volumetric
Efficiency means, select Engine Description.
Figure 2.20 Typical Calculation Menu
All specs except Vol Eff are now enabled
(printed in black, not gray). All you have to do is
pick a general description of your engine for the
Desc. input. Since you are using a 350 Holley 2
barrel carb with no restrictor plate, but “better
than stock” heads pick “350 2BBL - Ported
Heads” as the description.
You would be ready to Use Calc Values if the
RPM at Peak HP was correct. From reading the
comments in this menu, you see that a good
estimate of RPM at Peak HP could be around
5500 for an engine with a 350 CFM 2 barrel
carb. You now see the calculated Peak HP, Peak
Torque and Peak Torque RPM displayed at the
top of the menu.
If you click on Cancel, you will return to the
Engine Specs menu with the Power Curve specs unchanged. If you click on Use Calc Value, you will be
returned to the Engine Specs menu with a new power curve which includes the Calculated Peak HP, Peak
Torque, Peak HP RPM and Peak Torque RPM shown in this menu.
If you had changed the Cubic Inches from the 355 entered from the Engine Specs menu, you would also
be asked if the new Cubic Inches should also be used in the Engine Specs menu also.
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2.7.1 Calc Power Curve
This calculation is available from the Engine specs menu and lets you estimate an engine Power Curve.
Initiate this calculation by clicking on the “Calculate” menu item at the top of the Engine Specs Screen
Peak HP
Peak Torque, ft lbs
Peak Torque RPM
Figure 2.41 Calc Power Curve
Are the values calculate from these inputs. If you
select Vol Eff, the Peak HP value is calculated
using the following assumptions:
• 85% mechanical efficiency at RPM at HP
Peak
• 35% thermal efficiency
• Gasoline as the fuel with an energy content
of 19,000 BTU/lb
• Dry air density of .0764 lbs/cu ft (dry air at
29.92” and 60 degrees) .
The other Power Curve specs are derived from
Peak HP and RPM at HP Peak and an assumed
shape of the torque curve based on the Cubic
Inches. The RPM at HP Peak input at the bottom
of the menu is always loaded back into the
Engine specs menu.
These calculations are based on power corrected
to the standard aftermarket dyno correction factor
of 29.92” mercury and 60 degrees dry air. This is
the standard assumption used by the Circle Track
Analyzer for any power inputs.
Calc Based On
Click on this combo box to select from:
• Volumetric Efficiency %
• Engine Description
Depending on your choice, certain inputs will now be enabled.
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Engine Cubic Inches
Is the engine’s size in Cubic Inches. This is initially set to the Displacement in the Engine menu, but can
be changed to anything you want.
Vol Eff
Is the engine's volumetric efficiency at the HP peak. Volumetric efficiency means what is the amount of
air which this engine pulls in one cycle compared to how much it could under “ideal” conditions.
Generally this is less than 100%, but can be up to 130% for highly tuned race engines, or up to 300% on
supercharged or turbocharged engines. Generally, this is not the engine's peak volumetric efficiency
(which usually occurs at the torque peak) but is close to it.
Click on the down arrow of this combo box to select from the following choices:
• 65 Bad Production
• 75 Typ Production
• 80 Good Production
• 85 HiPerf Production
• 90 Poor Street/Strip
• 95 Typ Street/Strip
• 100 Good Street/Strip
• 110 Good Race Engine
• 115 Very Good Race Engine
• 120 Excellent Race Engine
• 125 Unrestricted Winston Cup
Desc
Is a general description of your engine. Note that the numbers for many descriptions are the CFM
rating of the carburetor, not the cubic inches.
RPM at HP Peak
Is the RPM at which the HP peak occurs. This is initially set to the RPM at HP Peak in the Engine menu,
but can be changed to anything you want.
Note: Most any modification which increases HP will also increase RPM at HP Peak. If you have no
information about your RPM at HP Peak, use an RPM 500 RPM lower than your highest RPM on the
track.
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2.7.2 Calc Displacement
Chapter 2 Definitions
Figure 2.42
2.22 Calc Displacement
This menu is available by clicking on the
Displacement Clc button in the Engine Specs menu.
When enough inputs have been entered, it shows
Displacement in Cubic Inches (which can be
transferred back to the Engine Specs menu by
clicking on Use Calc Value), Cubic Centimeters and
Liters.
Calc Based On
Click on this combo box to select from:
• Bore and Stroke
• CCs
• Liters
Depending on your choice certain inputs will now
be enabled.
Bore, inches
Is the Bore for this engine. Bore is the diameter of one cylinder.
Stroke, inches
Is the Stroke for this engine. Stroke is the distance the piston travels from TDC to BDC.
# Cylinders
Is the number of cylinders in this engine. For example, for a V-8 this would be 8.
Displacement in CCs
Is the total engine displacement in cubic centimeters (CCs) that you want converted to cubic inches. For
example, for a 1000 CC motorcycle engine, enter 1000.
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Displacement in Liters
Is the total engine displacement in liters that you want converted to cubic inches. For example, for a 5.0L
Mustang engine, enter 5.
Figure 2.43 Calc Weight %s
2.7.3 Calc Weight %s
This menu is available by clicking on any of the CLC
buttons by the Rear, Left or Cross Weight %s in the
Vehicle Specs menu. When enough inputs have been
entered, it shows Weight %s (which can be copied
back to the Vehicle Specs menu by clicking on Use
Calc Values), the Current Vehicle Weight in the
Vehicle specs menu (for comparison), and the new
Vehicle Weight based on the 4 corner weights entered
into this menu.
The weight measurements should be taken with the
driver in the car, all fluid and fuel levels in race
condition and on a very flat surface.
Left Front Weight, lbs
Right Front Weight, lbs
Left Rear Weight, lbs
Right Rear Weight, lbs
Are the weights on the respective tire in lbs. When you first open this menu, these are filled in with the
corner weights which produce the Weight %s for the Vehicle Weight currently entered in the Vehicle
Specs menu.
If you use the new weight %s from this menu, and the New Vehicle Weight is significantly different from
the current vehicle weight, you will be asked if you want to load the New Vehicle Weight into the
Vehicle Specs menu also.
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2.7.4 Calc C.G. Height
This menu is available by clicking
on the C.G. Height Clc button in
the Vehicle specs menu.
Figure 2.44 Procedure to Measure C.G. Height
The procedure to determine C.G.
height requires one end of the car
to be raised while accurately
measuring the wheel weights on
the other end of the car before and
after the car is raised. The
suspension must be blocked so the
springs do not compress during
the process. This can be done by
replacing the shocks with solid
links that maintain the vehicle’s
free standing height.
Block suspension (so springs can not be compressed).
Raise one end of car
a significant distance.
Weighing Scale,
show ing w eight level
and raised.
Block up tire level w ith scale
for accurate “ level car” w eight
Raising a typical car about 20 inches (quite a lot) will only show a weight increase of 30-60 lbs for most
cars. Therefore, this process requires very precise weight measurements. Some tips to improve the
accuracy of the procedure include:
• Wiggle the car slightly on the scale to ensure it always returns to the same weight.
• The higher you raise the car, the more weight difference you will see and the more accurate
results.
• The test should be run with the driver and all fluid levels at race conditions.
• Do the entire test more than once and average the C.G. height results.
This procedure can be dangerous if not done with care and using good
equipment. Take the proper precautions, especially if you raise the car
significantly.
Wheelbase, in
Wheelbase of the car in inches.
Total Vehicle Weight, lbs
The total weight of the vehicle, ideally with the driver and all fluid levels at race conditions.
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Figure 2.45 Calc C.G. Height
Total Front (Rear) Weight, lbs
The weight on the front tires (or rear tires if the front
of the car is raised) on level ground in pounds, before
the car is raised.
Raise Front or Rear
Choose which end of the car is raised for this test,
usually the rear.
Front (Rear) Tire Radius, in
The radius of the front tire (or rear tire if the front of
the car is raised).
Distance Raised, in
The distance the one end of the car is raised, in
inches.
New Total Front (Rear) Weight, lbs
The new weight on the front tires (or rear tires if the front of the car is raised) when the car has been
raised.
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2.7.5 Calc Rear Axle Ratio
This menu is available by clicking on the Rear
Axle Ratio Clc button in the Vehicle specs menu.
Figure 2.46 Calc Final Drive Ratio
Type
Click on this combo box to select from:
• Ring & Pinion Gear Only (typical of most
rear wheel drive rear axles)
• Quick Change with 4.56 Ring & Pinion
• Quick Change with 4.88 Ring & Pinion
• Chain Drive Only (typical of go carts, most
motorcycles, etc.)
• Gear Reduction & Chain Drive (typical of
motorcycles where there is a chain reduction
between the engine and the transmission, and
then there is the chain ratio between the
transmission and rear axle)
Depending on your choice certain inputs will now
be enabled, hidden or changed.
# Teeth, Pinion Gear
This is the number of teeth on the smaller pinion gear (or drive gear which attaches to the driveshaft) in
the rear axle. If you selected Gear Reduction & Chain Drive as the Type, this is the # teeth on the
sprocket or drive gear on the engine’s crankshaft. In almost all cases, this number will be smaller than #
Teeth Ring Gear.
# Teeth, Ring Gear
This is the number of teeth on the larger ring gear (or driven gear which attaches to the axle shafts
through the differential) in the rear axle. If you selected Gear Reduction & Chain Drive as the Type, this
is the # teeth on the sprocket or drive gear on the transmission input shaft or clutch shaft. In almost all
cases, this number will be larger than # Teeth Pinion Gear.
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# Teeth, Drive Sprocket
This is the number of teeth on the smaller drive sprocket on the engine or transmission for chain drive
systems. In almost all cases, this number will be smaller than # Teeth Wheel Sprocket.
# Teeth, Wheel Sprocket
This is the number of teeth on the larger driven sprocket on the wheel or axle for chain drive systems. In
almost all cases, this number will be larger than # Teeth Drive Sprocket.
Ring and Pinion Ratio
This is the ring and pinion ratio for the quick change, usually 4.56 or 4.88, but you can change this to
most any ratio.
# Teeth, Top Spur Gear
This is the number of teeth on the upper (top) spur gear in the quick change.
# Teeth, Bottom Spur Gear
This is the number of teeth on the lower (bottom) spur gear in the quick change.
2.7.6 Calc Frontal Area
This calculation is available from the Vehicle Specs menu and allows you to estimate a vehicle's frontal
area.
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Track Width, inches
Chapter 2 Definitions
Figure 2.47 Calc Frontal Area
Is the distance from the center of one front tire to
the center of the other front tire. This value is
initially set to the Rear Track Width in the Body
and Axle specs menu, but can be changed to most
anything you want.
Roof Height, inches
The distance in inches from the ground to highest
portion of the roof or vehicle in inches which
extends nearly the full width of the vehicle.
For example, for a truck with a roll bar behind the
cab, measure to the top of the roll bar, but not to
the top of one of the spot lights mounted on the
bar. However, if so many lights are mounted on
the bar that they are nearly continuous for the full width of the vehicle, it may be more accurate to then
measure to the top of the spot lights.
2.7.7 Tire Circumference
Tread Width
This calculation is available from the Wheel & Tire Specs menu and allows you to estimate either a front
or rear wheel’s Tire Diameter and Tread Width for certain Tire Rating Types.
Note: For all Rating Types except Rolling Radius, the Calc Tire Diameter is approximately 3% less than
what you would calculate based on the exact dimensions. This is to allow for some tire wear,
deformation, and slip.
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Figure 2.48 Calc Tire Circumference
Rating Type
Click on this combo box for the following rating
types:
• P-Metric (ex P225-60-15)
• Letter (ex G-60-15)
• Rolling Radius, inches
• Diameter, inches
Depending on your choice, certain specs will
become enabled. If you choose the P-Metric or
Letter Type, you will also be able to calculate the
Tread Width.
P Metric Tire Size (ex 225)
Identifies the tire's cross sectional width in
millimeters and is also related to the tire's load
carrying capacity.
Letter Tire Size
Identifies the tire's load carrying capacity. Click
on this combo box to select on of the letters. This
is an older rating system and there is more variation across manufacturer's.
Aspect Ratio
Is the ratio of tire cross sectional height
to cross sectional width. A 75 series
tire has a height 75% as high as its
cross sectional width, and is generally
a tall tire. A 50 series tire is a lower
profile tire, more suited to cornering
and performance.
Figure 2.49 Rolling Radius
Circumference
Diameter
Radius
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Wheel Rim Diameter
Is the diameter of the wheel's rim.
Rolling Radius, in
Is the tire's radius, measured with the tire mounted on the car, with the tire on the ground with typical
vehicle weight on it. Radius is the distance from the center of the tire to the ground. See Figure 2.49.
Diameter, in
Is the tire's diameter measured in inches. Diameter is the distance across the tire.
2.7.8 Estimated Traction Factors
This Calculation menu is available by clicking on the Traction Factor Clc button in the Vehicle specs
menu. Click on the combo box to be presented with general choices describing traction, and the
corresponding Traction Factor in %. This menu is different than other Calculation menus in that there is
not calculation performed, but you are simply picking a Traction Factor from a list of descriptions.
The Traction Factors in this list are very general.
You will probably have to fine tune this spec
based on your vehicle's actual lap times. The
program can also determine Traction Factor with
the Match My Lap Times command at the Main
Menu.
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Figure 2.50 Traction Factors
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2.7.9 Calc Spring Rate
Chapter 2 Definitions
Figure 2.51 Calc Spring Rate
This Calculation menu is available by clicking on
the Spring Rate Clc button in the Front
Suspension or Rear Suspension menu.
Spring Location
Click on this combo box to select which spring
location you are calculating a spring rate for,
either the Left spring, Right Spring or both
springs.
Type of Spring
Click on the combo box for Type of Spring to
change the inputs in this menu for the 4 basic
types of springs:
• Coil Springs
• Leaf Springs
• Solid Torsion Bars
• Hollow Torsion Bars
These inputs will be discussed in the 3 sections
below
Coil Springs
Wire Diameter, in
Is the diameter of the wire which makes up the coils, in inches. Take this measurement carefully as it has
a large impact on the results.
Inside Diameter of Coil, in
Is the inside diameter of the wire coils which makes up the spring, in inches. The coil diameter ranges
from 1.5 to 5 inches for most springs.
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Number of Active Coils
Is the number of active coils in the spring. Usually the top and bottom coils of a spring do not move (are
not active) and do not contribute to the “springiness” of the spring. Therefore the number of active or
moving coils is usually 2 less than the total number of coils. For example, for a spring with 12 coils, the
Number of Active Coils would be 10.
Leaf Springs
# of Leaves at Center
Is the number of individual leaves at the center of the leaf spring, where the axle attaches. For a single
leaf this would be 1.
# of Leaves at Ends
Is the number of individual leaves within 2 inches of the front and rear mounting points on the vehicle
frame. Usually this is 1.
Spring Length, in
Is the length of the main leaf spring in inches, usually 20 to 60 inches.
Thickness of One Leaf, in
Is the average thickness of each individual leaf, in inches. Take this measurement carefully, as it has a
large impact on the results.
Spring Width, in
Is the average width of each leaf, in inches. This usually ranges from 1 to 3 inches.
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Torsion Bars
Torsion Bar Diameter, in
Circle Track Analyzer
Chapter 2 Definitions
Figure 2.52 Torsion Bar Specs
Arm Length
Is the outside diameter of the section of the
bar which is designed to twist, in inches.
Take this measurement carefully as it has a
large impact on the results. See Torsion Bar
Length below.
Bar Outside Diameter
Active Bar Length
Torsion Bar Length, in
Is the length of the bar which is designed to
twist, which is usually the thinnest part of the
bar. See Figure 2.52.
Detailed Side View of Arm Length
Lever Arm Length, in
Arm Length
Is the distance from the bar to where the bar
attaches or rests on the axle. See Figure 2.52.
For the Front Suspension, this is usually the
length of the lower A Arm, from the center of
the torsion bar to the ball joint.
Axle Housing
Bar Inside Diameter, in
Is the inside diameter of the torsion bar if you have selected a Hollow Torsion Bar, in inches.
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2.7.10 Calc Roll Bar Rate
Chapter 2 Definitions
Figure 2.53 Calc Roll Bar Rate
This Calculation menu is available by clicking on the
Roll Bar Rate Clc button in the Front Suspension
menu.
Type of Bar
Click on this combo box to select from the following
3 types of roll bars:
• No Sway Bar
• Solid Bar
• Hollow Bar
Bar Outside Diameter, in
Is the outside diameter of the section of the bar
which is designed to twist, in inches. Take this
measurement carefully as it has a large impact on the
results.
Figure 2.54 Roll Bar Measurements
Production Style Bar
Custom Style Bar
Bar Outside Diameter
Arm Length
Active Bar Length
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Bar Outside Diameter
Arm Length
Active Bar Length
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Bar Inside Diameter, in
Is the inside diameter of the torsion bar if you have selected a Hollow Roll Bar, in inches.
Active Bar Length, in
Is the length of the bar which is designed to twist, which is usually the thinnest part of the bar. See
Figure 2.54.
Arm Length, in
Is the distance from the bar to where the bar attaches to the suspension. See Figure 2.54.
2.7.11
Calc Dew Point, deg F
Depending on your choice of Method of Recording Weather Data, you will be entering either Dew Point
or Relative Humidity in the Running Conditions menu. These humidity inputs at all these menus have a
Clc button. This is the Calculation Menu you will get if you are using Dew Point.
Know Relative Humidity?
Figure 2.55 Calc Dew Point
If you know the relative humidity of the air and
the air temperature, select Yes. Otherwise select
No to input Wet and Dry bulb temperatures from
a psychrometer. Depending on your choice the
appropriate inputs are enabled.
Outside Air Temp, deg F
Is the outside air temperature when the relative
humidity measurement was made. For example,
if the weather service or weather report gives a
relative humidity of 56 % and a temperature of 68
degrees, use 68 degrees.
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Outside Rel Humidity, %
Is the air's relative humidity as reported by a weather service or measured by humidity instruments.
Dry Bulb Temp, deg F
Is the temperature of the dry bulb thermometer on the psychrometer in degrees F. This is also the
temperature of any thermometer mounted in the shade when the Wet Bulb Temp reading is taken. The
Dry Bulb Temp must not be less than the Wet Bulb Temp.
Wet Bulb Temp, deg F
Is the temperature of the wet bulb thermometer on the psychrometer in degrees F. The wet bulb has a
"wick" or cloth covering the bulb which is moistened with water. The dryer the air, the greater the
difference between the wet and dry bulb readings. Relative humidity or dew point can be manually read
off a Psychometric chart from these two readings. This calculation replaces reading the chart. The Wet
Bulb Temp must be less than the Dry Bulb Temp.
Figure 2.56 Calc Relative Humidity
2.7.12 Relative Humidity, %
Depending on your choice of Method of Recording
Weather Data, you will be entering either Dew Point or
Relative Humidity in the Running Conditions menu.
These humidity inputs at all these menus have a Clc
button. This is the Calculation Menu you will get if
you are using Relative Humidity.
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Know Dew Point?
If you know the dew point of the air and the air temperature, select Yes. Otherwise select No to input
Wet and Dry bulb temperatures from a psychrometer. Depending on your choice the appropriate inputs
are enabled.
Outside Air Temp, deg F
Is the outside air temperature when the Dew Point measurement was made.
Dew Point, deg F
Is the air's Dew Point in degrees F as reported by a weather service or measured by humidity instruments.
Dry Bulb Temp, deg F
Is the temperature of the dry bulb thermometer on the psychrometer in degrees F. This is also the
temperature of any thermometer mounted in the shade when the Wet Bulb Temp reading is taken. The
Dry Bulb Temp must not be less than the Wet Bulb Temp.
Wet Bulb Temp, deg F
Is the temperature of the wet bulb thermometer on the psychrometer in degrees F. The wet bulb has a
"wick" or cloth covering the bulb which is moistened with water. The dryer the air, the greater the
difference between the wet and dry bulb readings. Relative humidity or dew point can be manually read
off a Psychometric chart from these two readings. This calculation replaces reading the chart. The Wet
Bulb Temp must be less than the Dry Bulb Temp.
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2.8 Match My Lap Times
The Circle Track Analyzer will automatically 'fine tune' certain critical specs to match a particular
vehicle's lap times. See Example 4.2. The Match My Lap Times process consists of:
1.
2.
3.
4.
You set all specs to match the vehicle you are building as close as practical. This is very
important for accurate results.
Click on the Match My Lap Times button at the top of the Main Menu to bring up the Match My
Lap Times menu shown in Figure 2.57.
Fill in the Match My Lap Times menu with your vehicle's performance. Then click on OK
(adjust veh. specs to match performance) to start the process.
The program will adjust:
• Engine Power Curve
• Tire Traction Factor
• Tire Type, if it needs more
traction than 100% Traction
Figure 2.57 Match My Lap Times Menu
Factor can provide
• Driver Aggressiveness
• Track Bank Angle
• Track Infield Width
To find a combination giving the
closest match to the vehicle's
performance.
If the program can not arrive at acceptable
specs in 100 passes around the track, it will
give you a notice. You may then want to
double check your entries in the Match My
Lap Times menu or some of the other specs in
the other menus.
If the program does arrive at acceptable specs,
you will be shown a summary of the new
specs the program found and how close the
program matched performance, as shown in
Figure 2.58. You can then load these specs
into the menus for this vehicle.
This process can save a good deal of "cut and
try" on your part to get your vehicle specs
adjusted. Example 4.2 shows the Match My
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Lap Times process in more detail.
Lowest Engine RPM in Turns
Enter the lowest RPM you see in the turns. This gives the program an idea of how slow the car must go
to make the turn.
Highest RPM Before Braking
Enter the highest RPM you see immediately before you brake. This gives the program an idea of how for
you get into the corner before you brake, and some idea of the shape of the power curve.
Lap Time
Enter the car’s lap time for
this particular track.
Figure 2.58 Results of Match My Lap Times
Adjust Power
Curve if Needed
Pick Yes and the program
will not only adjust vehicle
specs and track specs, but
also the engine power curve
to match lap times. This is
recommended when you do
not have a dyno curve for
the engine.
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Chapter 3 Output
The Circle Track Analyzer provides several ways to view and output the test results, including:
• Tabular, calculated Test Results displayed on the screen. Check Section 2.6 for definitions of Test
Results.
• Analyze Suspension is a powerful, graphical suspension analysis tool
• Analysis Report giving tips, warning of safety issues, etc.
• High resolution graphs
• Printer output or reports or graphs
• Vehicle Library for recording sets of vehicle specs for later use
Figure 3.1 Output Options from Test Results Screen
Menu Bar showing names of options
Vehicle File Name
Click on
and slide
slide bar
button to
display all
Test
Results.
History Log
Click on
and slide
slide bar
button to
display
entire
History
Log.
Performance Summary
Notes Summary and Notes button giving performance tips
Command Option Buttons
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Figure 3.2 Additional Output Options
Click here or here to graph these results
Click here or here to print these results
Click here to analyze the suspension as the car goes
around the track, as described in Section 3.6.
Click here to create Analysis Report (giving
performance tips) as described in Section 3.1
Click here for History Log options
Click here for help on Test Results
Click here to view and/or edit the Vehicle Comments, or the
Engine, Front Suspension or Rear Suspension comments
Click here to return to the Main Menu
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3.1 Analyze Perf. Reports
When calculated test results are displayed on the screen, you can obtain an Analysis Report by clicking
on Analyze Perf. in the menu bar. The Analysis report consists of 1-3 pages of suggestions for
improving performance, safety warnings, etc. concerning the performance results calculated. See Figure
3.3 and 3.4 for examples.
Figure 3.3 First Portion of Analysis Report
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IMPORTANT: The Circle Track Analyzer can NOT anticipate all
UNSAFE and poor performing situations. Do NOT rely only on the
Analysis report to point out problems and SAFETY HAZARDS. You
must use your own judgment, expert advice from experienced
engine builders and the manufacturer of the components.
Figure 3.4 Another Portion of Analysis Report
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3.2 Graphs
Graphs are obtained by clicking on the Graph button or the Graph name in the menu bar as shown in
Figure 3.1. Figure 3.5 shows a typical graph and a descriptions of some of the basic graph screen items.
Figure 3.5 Basic Graph Screen Items
Command buttons perform action as pictured with 1 click of mouse.
Menu bar provides for several graph commands and options.
Graph Title: change by clicking on Format, then Edit Titles/Legend.
Name of current Engine File
Commands to graph the current test results with
past test results. Last is the previous test results,
History are up to 6 results from the History Log.
Graph Legend,
which describes
the data graphed.
This includes
Name of test
results, Type of
Data. You can
also click on Data
Type names and
the corresponding
data line will flash.
This is useful to
find a particular line
when several are
graphed. Names
in the Legend can
be changed by
clicking on Format,
then Edit Titles/
Horizontal X axis. The scaling of this axis can be easily
changed as described in this section.
Grid lines. The style or elimination of grid lines can be changed by
clicking on Format, then Grid Style.
Data graph lines. The style and thickness of these lines can be
changed by clicking on Format, then Line Style.
Vertical Y axis, the scaling of which can be changed as described in this section.
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There are 2 basic types of test data which can be graphed:
• MPH
• Accel Gs
• Engine RPM
• % Throttle
• Downforce
• Cornering Gs
Vs (on X axis), either:
• Time in Seconds
• Distance if Feet
There are 3 basic types of tests which can be graphed:
• Current test results. These are the test results displayed in the Test Results screen, for the
current Vehicle specs.
• Last test results. These are the test results from the previous calculation. By comparing the
current calculated results to the last results, you can easily watch how each modification has
effected performance.
• Test results from the History Log. The History Log is a list of 25 tests, some of which you
have specified you want saved long term, some of which are simply some of the last tests you
have run.
Data_To_Graph
You can switch between data types as shown in Figure 3.6.
Figure 3.6 Switching between Data Types
98
Click on Data_to_Graph
for drop down menu.
Then select type of data
to graph, and what to
graph against (time or
distance for the X axis).
Your current choices are
shown with check marks.
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Graphing Current, Last and History Log Test Results
The Current and Last Test Results were defined earlier. The History Log is explained in some detail in
Section 3.5 starting on page 112. This section will explain how to graph test results for tests in the
History Log.
Figure 3.7 History Log (see Section 3.5 for more details)
Click on the History Button or the History
menu item todisplay the History Log.
Click in this column to
show Yes or remove
Yes. Tests marked Yes
will be graphed.
This column shows name
program will display in graph
Legend for this test. Click on
name to change it.
Choose a ‘Graph’ option
from the menu bar to close
the History Log and graph
the tests identified by the
menu option you pick.
Click and drag slide bar to display entire
History Log. Some tests marked Yes
may be at the bottom of the Log and not
be visible now.
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Other Graphing Features
The graph screen has several features, including:
• Printing
• Cursor to pinpoint the value of a particular point on the graph
• Changing titles and legend names
• Changing the scales
• Miscellaneous Format Options to change the appearance of the graph.
These are discussed in this next section.
Printing
Figure 3.8 shows the options for printing graphs and how to access these options. It also shows the
screen for changing the Windows Printer Setup.
Figure 3.8 Printing Graphs
Clicking on the Printer button is the same as clicking on File and then Print.
Click on File to display the two print menu options
Click here to print the graph with solid lines. This
works best for printing graphs in color.
Click here to print the graph with dashed lines. This
works best for printing graphs in black and white,
where different dashed line styles let you distinguish
between different graphs.
Click here change the printer or printer driver,
page orientation, etc. as shown below.
Windows standard
Printer Setup menu
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Cursor
The cursor feature is very useful for determining or comparing the value of the graph lines at various
places. See Figure 3.9 for explaining the use of the cursor.
Figure 3.9 Cursor Features and Commands
Click here to turn Cursor On
Cursor line,
usually pink or
green,
depending on
background
l
Click here to turn Cursor Off
Click on these buttons to move the cursor left or
right. Hold down the <shift key> while clicking
these buttons and the cursor moves farther.
You can also enable the cursor by clicking on
View, then Turn Cursor On.
The value of each
graph line at the
cursor is
displayed here.
The X value of the cursor is shown here,
in this case the RPM of 7.5 seconds
You can also enable the cursor by single clicking on a graph line at a
data point. This also provides a quick way to move the cursor from 1
area of the graph to another. (Do not drag the mouse while clicking or
you will zoom in on that area.) If you click on a graph line in between
data points, the cursor will not appear.
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Changing titles and legend names
Many times you may want to customize a graph by printing labels of your choice. Click on Format and
then Edit Titles/Legend to bring up the menu shown in Figure 3.10 which will allow you to do this.
Figure 3.10 Menu to Edit Title and Legend
This is the list of Standard names the program uses unless you
click on the Use New Titles button below. Select (click on) a
Standard name you want to change. The Standard Name
appears in the edit box, along with the current New name if there
is one. Once you have selected a name from this list (that
row will be highlighted) it is easier to use the up and down
arrow keys to select the next item to edit than clicking the
item with the mouse.
This is the list of New
names the program will
use if you click on Use
New Titles. If a title in
the List of New Names
is blank, the program
will use the Standard
name.
Standard name from
row selected.
New name for you to
edit. Other options
include clicking on
the Copy Std Name
to New or Blank Out
New Name buttons.
Click here to close this
menu and use the New
names you have
entered. Where New
names have been left
blank, the Standard
name will be used.
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Changing the scales
Many times you may want to change the scale of the X or Y axis. This may be to show an area in more
detail or to match the scales of a previous graph. The Engine Analyzer has several ways to change the
scales as shown in Figures 3.11 and 3.12.
Figure 3.11 Changing Scales for the X or Y Axis
Clicking on these buttons zooms in or zooms out
on the graph, either vertically or horizon-tally
Hold down the shift key to produce faster action
Clicking on these buttons shifts
the graph left, right, up or down.
Hold down the shift key while
clicking produces faster action.
Click here to restore “autoscaling”. That is where the
computer picks the scale
to show all the graph in
good detail.
Click on View, then
either Zoom or
Specify Scales
(axes), or the Set
Scales button to
obtain the menu
shown in Figure
3.12 on the next
page.
You can use the mouse to outline an area to be zoomed in on. Simply click on the
mouse key in the upper left corner of the area, then hold the key down and drag
the mouse to the lower right corner of the desired area. A box will be drawn as
shown. When you release the mouse key, this area will fill the whole graph. This
feature is disabled if the cursor is turned on. Also, start the upper left corner well
away from a graph line or the program may turn on the cursor instead.
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Figure 3.12 Menu to Specify Graph Axes Scales
This menu can be obtained 2 ways. You can click on View in the
menu bar then Specify Scales (axes), or click on the Set Scales
button, the right most button on the screen. See Figure 3.11.
The current scale limits
are loaded when this
menu opens. Change
any or all these to most
any value you want.
Either the left (Time) or
right (Distance) section
will be enabled
depending on what is
graphed on the X axis.
Click on OK to have
the graph redrawn to
these new scale limits
Format Options
Click on the Format menu item to be presented with several options which will be briefly discussed here.
Line Style
Click on Line Style to change the thickness
of the graph lines.
Grid Style
Click on Grid Style to change or omit the
drawing of grid lines on the graph.
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Figure 3.13 Format Options
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Back Color
Click on Back Color to change the background color of the graph from white, black or gray.
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3.3 Vehicle (& file) Library
The Circle Track Analyzer allows you to save a set of vehicle specifications to the Vehicle Library under
a name of your choosing. You can then open these vehicles out of the Vehicle Library in the future for
comparison or modification. The Open window is shown on the next page with explanations.
Note: You can also save sets of Engine, Front Suspension, and Rear Suspension specs to their own
separate libraries. This is done very similarly as with the Vehicle Files, except you click on File, then
Open from the individual Engine, Front Suspension, and Rear Suspension menus.
Figure 3.14 Vehicle Library Options
Click on Open button (or ‘File (vehicle)’, then ‘Open’) to display Vehicle Library
shown here. (Save option also available after clicking on ‘File (vehicle)’.)
Click on Save button to save current Vehicle specs to Library
Total # Vehicles
in Library
Name of chosen
Vehicle (currently
highlighted in
Vehicle List
Preview of
Vehicle chosen
Click and drag
slide bar to view
all vehicles in list
Click here to
open the chosen
Vehicle
Click here to delete
chosen Vehicle.
Click here to close the Vehicle Library with
No changes (without opening a vehicle)
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Single click on
vehicle to
choose it for
preview. Double
click to immediately open it.
Click here to bring up standard
Windows File Open screen, to let you
open a file in most any folder
(directory) and disk drive.
Click here to bring up on screen
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Open a Vehicle File
To open a vehicle file saved in the Library, either:
• Click on the Open button
• Click on the “File (vehicle)” menu item and then on the “Open Vehicle” options from the list.
You will obtain the window shown on the previous page. Single click on one of the vehicles in the list,
or click and drag the slide button on the right side of the list to display more vehicles. Once you single
click on a vehicle, it is now the Chosen Vehicle File and a preview of the vehicle is given in the Preview
section. If the file you chose was not a valid Circle Track Analyzer file, the program will tell you and
you can not choose it.
Once a vehicle has been chosen, you can delete it by clicking on the Delete button, or Open it by clicking
on the Open button in this window. You can also click on a different vehicle to Preview it or close this
window and return to the Main Menu without choosing a new vehicle file.
If you are sure of the vehicle you want to open, you can simply double click on it from the Vehicle List.
This opens the vehicle without a preview and closes this menu.
Figure 3.15 Engine File Options
Current Engine File Name
Click on File in the Engine, Front Suspension or
Rear Suspension menus to Open a set of saved
specs, or to save the current set of specs in just
that screen. This allows you to build libraries of
Engines, Front Suspensions and Rear
Suspensions for easily building other complete
vehicles in the future.
• New blanks out the current specs and
comments.
• Open Example opens a library of example
specs provided by Performance Trends.
• Open Saved opens a library of specs you have
saved.
• Save saves the current specs to the same
name as these specs are currently called.
• Save As saves the current specs to a new
name that you will enter.
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Save a Vehicle File
Before we discuss saving an engine file, it is important for you to understand how the program opens and
uses vehicle files. When you open a vehicle from the Vehicle Library, you are only using a copy of the
vehicle. The original vehicle file is kept in the library.
As you make changes to the vehicle, they are only made to this copy. The original file is not changed. If
you want to delete your changes, you can simply open a fresh, unchanged copy of the original vehicle file
from the Library. If you want to keep your changes, you must save them. This can be done by clicking
on the Save button. You are also asked if you want to save your changes whenever you open a new
vehicle, and the program has detected you have made changes to the current file.
To save a Vehicle File, you will be presented with the Save Window as shown below. The program
suggests a new vehicle name which is the same as the current vehicle name shown at the top of the Main
Figure 3.16 Saving Vehicle File Options
Click on Save button to bring up this Save menu.
Click here to save specs to New Vehicle name shown
New name to save vehicle specs to.
Leave unchanged and click OK to save
to the current vehicle name. Click on
name in box to change it, then click OK
to save it to the new name.
Name of current
vehicle file you
are working with
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Menu. If you want to save your changes to the same name, simply click on OK. This will update the
current vehicle file with your latest changes.
If you want to save the current set of vehicle specs with your changes to a new name (and leave the
current vehicle file in the Library unchanged), then click on the suggested file name and modify it as you
want. For example, in the window shown on the next page, you may want to add -2 to the current name
MUSTANG to create MUSTANG-2 to indicate this is the 2nd revision of MUSTANG. This is the safest
way to make changes, because you can always return to an earlier version and see what you had done.
Certain file names are not acceptable, including:
•
•
•
Names with more than 3 characters to the right or 8 characters to the left of a period (.) .
Names over 11 characters long (12 characters if one is a period).
Names which include the characters:
/ \ [ ] : | < > + = ; , * ? or spaces
•
Names with lower case letters. These letters will be converted to upper case once the file is saved.
Vehicle files are saved in the CTADATA subdirectory in the CTA20 subfolder (subdirectory) under
PERFTRNS.PTI folder (directory). Unlike earlier DOS Circle Track Analyzer programs, you can copy
Windows Circle Track Analyzer files from programs on other computers to this folder (directory) and
they will be found by the program.
The method of saving Engine, Front Suspension and Rear Suspension files is exactly the same as
complete Vehicle Files, except that you access the Save menu by clicking on File at the top of these
individual menus, as shown in Figure 3.15. These files are saved to the ENGINE, FRONT or REAR
folders (directories),
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3.4 Printer Output
The Circle Track Analyzer can print the tabular test results for a permanent hardcopy by clicking on Print
in the menu bar or the Printer button. The menu of options shown in Figure 3.17 will appear. Check the
options you want to use for the printout by clicking on any or all of the top for boxes. All options and
buttons are discussed in this section.
Figure 3.17 Printer Command and Menu of Printer Output Options
The Windows Printer Setup
option lets you choose the
printer or printer driver being
used by Windows and also
the page orientation.
Click on Print or
the Printer
Button for the
Printout Options
menu shown to
the right.
Include Vehicle Specs
Select this options if you want all the current Engine specs, Vehicle specs, etc printed with the results.
This will add 1 or more pages to the printed report.
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Include Vehicle Comments
Select this option if you want all the comments for the complete vehicle printed with the results. These
are the comments which appear on the Main Screen. Requesting this option may require some results to
be printed on a second page.
Request Report Comment
Select this option if you want to be asked for a comment for each particular report you send to the printer.
These "report comments" are useful to identify important points for future reference, like modifications,
weather conditions, etc. Requesting this option may require some results to be printed on a second page.
Include Eng & Susp Comments
Select this option if you want all the comments for the Engine, Front Suspension and Rear Suspension
printed with the results. Requesting this option may require some results to be printed on a second page.
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3.5 History Log
The Circle Track Analyzer remembers the results and the Vehicle specs which produced those results for
up to the last 25 runs you have made. This can be a very handy comparison of one run to another and
saves you the trouble of making notes on pieces of paper. It is also handy to be able to go back to some
condition which gave very good performance, but you don’t remember why or what the specs were.
Figure 3.18 shows the History Log and options.
Figure 3.18 History Log and Options
Click on History for History Log
Click on Test
Title to
change the
Title or
retrieve the
specs which
produced
these results.
History Log
is displayed
below the
columns of
test results.
Click and
move slide
bar to
display all
25 tests in
the History
Log.
The History Log can be displayed from either the Test Results screen shown in Figure 3.18 above or in
the Graph screen as shown in Figure 3.19 on the next page. The Log is presented slightly differently in
each instance, showing and hiding columns which are most appropriate for each use.
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Chapter 3 Output
Figure 3.19 Clicking On Test Title
Click on Test Title and you are asked if you want
to retrieve the specs which produced these
results. Answer Yes and the specs are retrieved.
Answer No and you can then change the Test
Title. This is useful for making notes about this
particular run, modifications you made, etc.
Graph?
Click in this column to have a Yes inserted or removed. All test rows with a Yes will be graphed if you
click on Graph These Tests in the menu bar. This column is only visible in the History Log displayed in
the Graph screen. See Figure 3.20.
Figure 3.20 History Log from the Graph Screen
Graph Title
Is the title which will appear in the graph legend for this test. The program creates a simple title based on
the Engine File Name and the time the test was run, but you can click on this name and the program will
ask you to enter a new name, perhaps something like “3 in Stagger”. This column is only visible in the
History Log displayed in the Graph screen. See Figure 3.20. The first time you type in a Test Title, the
Graph Title will be changed to the first 16 letters of the Test Title.
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Save?
Click in this column to have a Yes inserted or removed. All tests move toward the bottom of the log as
new tests are run, and eventually fall off the list. However, tests with a Yes move to the bottom, but do
not fall off the list and are saved on the list until you remove the Yes in this column.
Tip: If you want to save a test, but do not necessarily want it on the History Log,, click on it to retrieve it
and the engine specs which produced it. At the Main Screen, make notes of what this test and engine are.
Then save it to the Vehicle Library. Although the test results are not available for graphing, you can
open this engine file and recalculate the test results at any time in the future.
Lap Ft
Is the Lap Distance in feet for these results. This is useful for determining if you are making an “apples
and apples” comparison. If the Lap Ft is different, then you should expect different lap times.
Infield
Is the Infield Width in feet for these results. This is useful for determining if you are making an “apples
and apples” comparison. If the Infield Width is different, then you should expect different lap times.
MnRPM
Is the minimum (or lowest) engine RPM in the turns.
MxRPM
Is the maximum (or highest) engine RPM right before braking.
Lap Time
Is the Lap Time is seconds.
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Imp.
Is the improvement in Lap Time for this test compared to the test below it, usually the previous test run.
If Lap Time is longer, the Imp. will be negative.
MPH
Is the average MPH for this test.
Imp.
Is the improvement in MPH for this test compared to the test below it, usually the previous test run. If
MPH is lower (slower), the Imp. will be negative.
Car Length
Is the improvement in Lap Times expressed in car lengths. The program assumes about 20 feet for a car
length. If the Lap Time is longer (slower), the Car Length will be negative.
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3.6 Analyze Suspension
A powerful feature of the Circle Track Analyzer is its ability to predict suspension movement, cornering
forces, performance and weight transfer as the vehicle goes around the track. This information is
displayed in the Suspension Analysis screen shown if Figure 3.21. You obtain this screen by clicking on
Analyze Suspension at the Test Results screen.
Check Appendix 5 for significant, new options/outputs for this feature.
Figure 3.21 History Log and Options
Front Suspension shows how suspension is moving as vehicle travels around track.
Graphic showing
Menu commands
Click here to
estimated RPM, throttle
for various options.
close this
and braking position.
Estimated spring
compression
(jounce) or
elongation
(rebound,
reported as a
negative ‘-’
number).
Tire load in
pounds, and bar
graph of tire
load. Black line
in bar graph
indicates static
load.
Static (car
standing still)
and Dynamic
Weight %s.
The “dot” shows the current vehicle acceleration
combination.
Friction Circle shows how much of the available tire traction is
being used (how hard the tires are being pushed).
Track postion shown with the MPH, distance and time for the current position.
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The only way to return to the program from this screen is by clicking on the [X] button at the
upper right corner, or the icon button at the upper left corner. (In Windows 3.1, click on the
[-] button in the upper left corner, then select Close.)
This screen is very important to understand how suspension changes will affect suspension motion, tire
camber, tire corner rates, roll center motion, all of which are critical for handling and fast lap times.
From this screen you can:
•
•
Watch the car's performance from the current Test Results.
Compare the current Test Results to a Baseline condition, some previous Test Results you told the
program to save as a Baseline. Baseline conditions are printed or drawn in pink so you can easily
see the difference between the Baseline and the Current conditions.
Note that Baseline conditions can only be displayed if the current Test Results and Baseline results are
for the same length track and same infield width. This is because the Baseline and current conditions are
compared and displayed for the same place on the track.
Another important feature of this screen is the Reports option. Reports give summary analysis of the
suspension and provide some 'starting point' recommendations for this suspension setup on this particular
track.
This screen is divided into 4 sections:
• Front Suspension (upper left corner)
• Total Vehicle (upper right corner)
• Track Position (lower left corner)
• Friction Circle (middle bottom)
These are discussed below:
Front Suspension (upper left corner)
This section shows how camber, instant centers, car dive and roll, and roll center change as the car goes
around the track. Tire camber is critical to getting the most traction out of your tires which is critical to
vehicle handling.
If you are also displaying the Baseline condition, the Baseline Roll, Dive and Cambers are printed in
pink, and the Baseline Roll Center position is drawn as a Pink dot.
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Total Vehicle (upper right corner)
This section shows how each corner of the car is working: how much weight is on each tire and how
much each spring is compressed (from jounce) or elongated (from rebound). The tire weights are
displayed with the bar graphs for easy comparisons.
Static and dynamic Weight %s are displayed in the center of the screen. Static Weight %s are what you
input in the Vehicle Specs menu. Dynamic Weight %s are based on the actual corner weights as the car
goes around the track. These depend on aerodynamic downforce, cornering forces, weight transfer, etc.
The top of the screen shows bar graphs for the % Brake and Throttle the program assumes the driver is
using. A tachometer is displayed showing how RPM is changing, with the actual RPM reading printed
below.
If you are also displaying the Baseline, Baseline spring compression and tire weights are printed in pink,
Baseline tire weights are graphed as a pink outline bar, and Baseline RPM is drawn on the tach and
printed.
Track Position (lower left corner)
This section shows the car's approximate position on the track. The results always start at the beginning
of Turn #2, and that is where the Yellow line (indicating the distance the car has traveled) also starts.
The position is only approximate because the track is drawn the same even if the actual track is long and
narrow (tight) or short and wide (open).
Printed inside the track is the MPH, distance in Feet, and elapsed time.
If you are also displaying the Baseline condition, the Baseline MPH, Feet, and Time are also printed.
Below the track an estimate is made of how far ahead or behind the Baseline condition is from the current
Test Results in Car Lengths.
Friction Circle (middle bottom)
A Friction Circle is a useful way to analyze how hard the tires are working in all 3 directions:
accelerating, cornering, and braking.
For example, if a tire has enough traction to provide 1 G of acceleration, it probably also has enough
traction to provide 1 G of braking and 1 G of cornering. If the driver has enough engine and braking to
accelerate and brake at 1 G, and if the driver was using all the available traction from this tire, you would
see his current acceleration "dot" somewhere on the 1 G circle. Any time the car was not on the 1 G
circle it would be an indication that the car was capable of more performance than what the driver was
asking of it.
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Things the would improve overall vehicle traction will increase the G level which can be sustained on the
vehicle, and therefore increase the G level you will see on the Friction Circle. This would include:
• More downforce, due to either banking or aerodynamic downforce.
• “Stickier” tires.
• Keeping the weight between all 4 tires as even as possible (not necessarily the case for dirt cars).
• Four wheel drive for accelerating.
• Optimum camber (however this is not simulated in this version of Circle Track Analyzer).
If you are also displaying the Baseline condition, the Baseline acceleration is graphed in pink.
Menu Options
Click on 'Options' to allow extension lines to be drawn or not drawn in the front suspension layout
screen, or to display or not display the Baseline conditions. Other options including slowing down or
speeding up the Continuous display of the results, or renaming the Baseline condition.
Click on 'Print' to print this screen, or change the Windows Printer Setup.
Click on 'Continuous' for a continuous display of the vehicle moving around the track. Click on 'Single
Step Ahead' or 'Single Step Back' to advance the results ahead or back 1 data point. This allows for more
detailed analysis and understanding of the results.
When you leave this screen you are asked if you want to save the current Test Results as the Baseline.
This is the only way to change the Baseline Condition.
Reports
One important Menu Option is the ability to produce Suspension Analysis reports, of 4 types:
• Suspension Calculations
• Suspension Calculations with Comments
• ‘Rule of Thumb’ Suggestions
• ‘Rule of Thumb’ Adjustments
These are discussed below.
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Suspension Calculations
Suspension Calculations with Comments
These reports show calculations concerning the suspension specs (some not found anywhere else in the
program) like Roll Stiffness Distribution, Roll Stiffness in degrees per G, etc. Table 3.1 gives
definitions of these calculations. The report “with Comments” includes the comments for the Front and
Rear Suspensions which you’ve entered at those screens.
Table 3.1 Suspension Calculations Definitions
Front Suspension
Spring Rate, lb/in
Motion Ratio
Motion Ratio Squared
Spring Angle, deg
Wheel Rate, lb/in
Instant Center Height, in
Instant Center Arm from Tire, in
Scrub Radius, in
Roll Bar Rate, lb/in
Roll Bar Motion Ratio
Roll Bar Motion Ratio Squared
Roll Bar Rate at Tires, lb/in
Natural Frequency, cycles/sec
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Front Spring Rate from the Front Suspension Specs menu.
See pages 31-40.
Motion Ratio for Spring is the ratio between an inch of spring
motion to wheel motion. This ratio is corrected for the instant
center location, which makes this calculation more accurate
and possibly different than what other programs would
calculate.
Motion Ratio squared for Spring. See Motion Ratio above.
Spring's installation angle. See Front Suspension Specs
Definitions. See pages 31-40.
Spring rate at tire. See list of Definitions in Front Suspension
Specs Screen. See pages 31-40.
Height of Instant center of that side of the suspension. See
Front Suspension Specs Screen Definitions. See pages 3140.
Distance from the tire's centerline to the Instant center of that
side of the suspension. See Front Suspension Specs
Screen Definitions. See pages 31-40.
Tire's scrub radius. See Front Suspension Layout Screen
Definitions. See pages 31-40.
Is the Roll Bar Rate from the Front Suspension Specs menu.
See pages 31-40.
Is the motion ratio of the roll bar, or what fraction of the tire's
motion at its centerline does the roll bar move. Like the
spring's motion ratio, this also corrects for the instant center
location of the suspension.
The square of the Roll Bar Motion Ratio. This is the fraction
of the Roll Bar Rate which is actually felt at the tires.
Roll Bar Rate times Roll Bar Motion Ratio Squared, or the
effective roll bar rate.
Is the number of cycles per second the car naturally wants to
bounce at. If you removed the shock and jumped on that
particular corner of the car, this is the number of bounces
you would see in 1 second. Soft sedans have lower
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Roll Center Height, in
Roll Center Offset, in
Front Roll Stiffness, ft lbs/deg
% Front Stiffness from Roll Bar
% Total Vehicle Roll Stiffness
Circle Track Analyzer
Chapter 3 Output
frequencies of 1 to 1.3 where race cars have frequencies of
1.8-2.2. Frequencies much higher than this would make the
driver's eyes blur and are extremely uncomfortable to the
human body.
Roll Center Height. See Front Suspension Layout Screen
Definitions. See pages 31-40.
Roll Center X location. See Front Suspension Specs
Definitions. See pages 31-40.
Is the amount of torque (ft lbs) applied to the car it takes for
the front springs to allow the car to roll 1 degree. A real car
will roll more than this due to compliance in tires, suspension
members, bushings, etc.
The % of the Front Roll Stiffness contributed by the roll bar.
The % of the Total Vehicle's Roll Stiffness contributed by the
front suspension. This usually ends up in the range of 7585% for front engine/rear drive cars.
Rear Suspension
Spring Rate, lb/in
Natural Frequency, cycles/sec
Roll Center Height, in
Rear Roll Stiffness, ft lbs/deg
% Total Vehicle Roll Stiffness
Rear Spring Rate from Rear Suspension Specs menu.
Natural frequency of the rear suspension. See Front
Suspension definitions above.
Height of the Rear Roll Center. Most all cars are designed
with the Rear roll center higher than the front, for improved
stability.
The roll stiffness of the rear suspension. See Front
Suspension definitions above.
The % of the Total Vehicle's Roll Stiffness contributed by the
rear suspension. This usually ends up in the range of 1525% for front engine/rear drive cars.
Total Vehicle
Vehicle Roll Stiffness, ft lbs/deg
Roll axis to CG ht Moment Arm,
in
Level ground roll rate, deg/G
CG Location:
Distance Behind Front Axle, in
The roll stiffness of the front and rear suspension. See Front
Suspension definitions above.
Is the height of the CG above the roll axis at the CG (center
of gravity) location. This is the lever which acts to roll the car
as the car corners. The greater this Moment Arm, the more
the car will roll. If this height is 0, the car will not roll at all (at
least from spring jounce/rebound). See Figure 3.22.
Is the amount of body roll in degrees produced from spring
jounce/rebound when the car corners at 1 G on level ground.
The actual car will roll more due to compliance in the tires,
suspension members, bushings, etc.
Is the distance toward the rear from the front axle (line
joining the center hubs of the left and right front wheels)
where the CG is located based on the Weight% Rear in the
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Distance from Vehicle
Centerline, in
Circle Track Analyzer
Chapter 3 Output
Vehicle Specs menu. See Figure 3.22.
Is the distance from the car's tire track centerline where the
CG is located based on the Weight % Left in the Vehicle
Specs menu. Note that this Centerline may not be the same
as the Drivetrain Centerline, on which your suspension
measurements are based.
Figure 3.22 Roll Axis to CG Height
CG Location: Distance behind front axle
‘Rule of Thumb’ Suggestions
This report gives some recommendations for
spring rates and front roll bar rate (based on the
desired wheel rates and knowing the motion ratios
and spring installation angles). It also compares
your car's roll center height and scrub radius with
typical values, and recommends a starting point
for rear tire stagger and cross weight.
Moment Arm
CG
Roll Axis
Front Roll Center
Rear Roll Center
As the beginning of the report states, these recommendations are based on general
racer experience and not detailed computer analysis of your particular set of
suspension specs or suspension layout. You will likely have to adjust these
recommendations to work with your particular car and driving style.
This report gives recommendations for spring rates, assuming the front and rear springs will be installed
into the same suspension geometry and angle as is currently specified. If you are going to change the
geometry or installation angles of the springs, do this first. Then obtain a new report of
recommendations.
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‘Rule of Thumb’ Adjustments
This report is a handy guide, listing vehicle modifications to correct various handling problems. The
modifications are listed with those usually having the most effect first. This report is exactly the same
each time it is printed and is based on racer and chassis builder experience. It is NOT based on computer
analysis of your particular vehicle or suspension specs.
Check Appendix 5 for significant, new options, reports and calculated outputs
for this feature.
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Chapter 4 Examples
Chapter 4 Examples
Each of these examples become progressively more complex, assuming you have performed and
understand the preceding example. Section 1.5's example is somewhat more basic than Example 4.1, so
it may be a better place to start if Example 4.1 looks complicated.
The results shown in these examples may be
somewhat different than what you obtain with
your particular version of the program That
is due to minor upgrades in the calculations
in later versions.
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Chapter 4 Examples
Example 4.1 Changing Axle
Ratio
Example 4.1 will be fairly simple to get you started. We will simulate a common modification, changing
the Rear Axle Ratio. We will see the effect on Lap Times, MPH, engine RPM range, etc.
First, start the Circle Track Analyzer program following the procedure in Section 1.4 by either:
• Clicking on the Circle Track Analyzer v2.0 icon in the Perf. Trends program group
(Windows 3.1)
• Clicking on Start, Programs, Perf. Trends, then Circle Track Analyzer v2.0 (Windows 95
and 98)
• Clicking on the CTA.EXE (CTA) program under the CTA20 directory (folder) under the
PERFTRNS.PTI directory (folder) using File Manager (Windows Explorer). (Terms in
parentheses are for Windows 95 and 98.)
You will be shown the Circle Track Analyzer’s Main Menu, Figure 4.1. Notice at the top of the screen
that the current Vehicle file is a LATEMODL. Although these specs may not match your car, follow
along to see how to use the program’s many features.
If it is not LATEMODL.355 (late model with 355 Chevy) or if you think the current car’s specs have
been changed, you can Open up this Vehicle file by clicking on the Open button as shown in Figure 4.2.
Open the Vehicle file LATEMODL.355 shown in Figure 4.2. If you have made any changes to the
vehicle which originally appeared at the top of the Main Menu, the program will first ask you if you want
to save these changes. Answer No and you will be returned to the Main Menu with the
LATEMODL.355 specs loaded into the program.
Click on the different categories of vehicle specs or the Running Conditions button on the Main Menu.
Since we want to see the effect of changing the axle ratio on this vehicle, we first need to get a "baseline"
test. A "baseline" is a performance test before the modification. Therefore, if you examine the contents
of any component menus, leave all current values as they are.
Click on the Running Conditions button and you will now be shown the Running Conditions screen.
This screen gives the conditions for calculating performance like track weather, the track specs, driver
preferences, etc. For now, leave these values as they are.
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Figure 4.1 Main Menu
Circle Track Analyzer
Chapter 4 Examples
Name of Vehicle you are working with.
Click here to
Calculate
Performance
in one step.
Click here to
show
Running
Conditions
and then
Calculate
Performance.
Proceed with the calculations by clicking on the Running Conditions button in this menu.
The program will display the Calculation Progress indicator as calculations progress. When the
calculations are finished, the performance results will look like Figure 4.3. You now see a screen with
columns of numbers describing the LATEMODL.355's run around half the track. The program assumes
the other half is exactly the same as the first half, so only calculates half a lap. At the top in the right
corner is a summary of the run and any improvement between the current run and the last run. The Last
run can be from the last time you ran the program. (The program remembers results from different
sessions, between computer shutdowns and start ups.)
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Figure 4.2 Vehicle Library
Name of Vehicle the
program is currently
working with. The
current specs may
have been changed
and be different than
the Vehicle in Library
of the same name.
Click on the vehicle
you want to Open to
see a Preview.
Double click to
Open immediately.
Preview of chosen
(highlighted) vehicle.
Click here to show
Vehicle Library
Figure 4.3 Test Results
Performance
Summary
showing Lap
Time & MPH.
Notes pointing
out important
things about
this run. Click
on Notes
button or
Analyze Perf
for more info.
Click here or
here to Graph.
Data columns
showing car
performance at
requested time
intervals.
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Note the Lap Time of 16.16 seconds with a MPH of 83.5 at the top of the report with the current 6.20
axle ratio. In the columns of numbers in the last row you see a time of 8.08 sec, exactly half of the lap
time of 16.16. This is because the program only calculates results fro half a lap, assuming the other half
of the lap would be exactly the same.
Other important things to look for in the Test Results screen include:
Notice that the Notes Summary is pointing out a couple of things: Low Lift Coef. and Engine
RPM High. If you click on the Notes button, you obtain the screen shown in Figure 4.4. These
notes can be useful for understanding your performance and safety considerations.
Figure 4.4 Notes Screen Produced by Clicking on the Notes Button
To obtain a graph of these results, click on the Graph button or Graph menu item. The program
will present a graph similar to that shown in Figure 4.5 of Engine RPM. If you do not see a
graph of Engine RPM, click on Data Types at the top of the graph and select Engine RPM.
Since the Notes pointed out Low Lift Coefficient, you might want to try the Downforce Graph
Data Type. Here you can see how much downforce in pounds the Low Lift Coefficient is
generating on this track. Note that track banking also generates downforce, and the
downforce is a combination of banking effects and aerodynamic effects.
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Figure 4.5 Engine RPM Graph
Click here for other options
Click here to change data to be graphed
Although
results are
calculated and
reported for
only half a lap,
graphs are
shown for the
full lap.
Figure 4.6 Graph of Downforce
Click on
Data_To_Graph,
then select data
type and data
type for X axis,
seconds or feet.
Check mark
shows current
selections.
Downforce is a
minimum on the
straightaway,
because banking
effect in turns is
minimum.
However,
program still
assumes
banking on
straightaway,
which reduces
f
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Changing the Rear Axle Ratio
Now for the good part; lets change the gear ratio and see what happens. Get back to the Main Menu by
clicking on Back in the menu bar (or pressing <ESC>) at the graph screen (Figure 4.5), then clicking on
Back (or pressing <ESC>) again at the tabular Test Results screen (Figure 4.3).
Click on Vehicle to bring up the menu shown in Figure 4.7. Because the Note in the program said the
Engine RPM was high, lets try a lower axle ratio, which will reduce the RPM range. Lets try a 5.9 axle
ratio as shown in Figure 4.7. With wrenches, money, parts and a race track, this could take several days.
On the computer we will be done in a few seconds, with clean fingernails and money left in our wallet!
Figure 4.7 Vehicle Menu for Changing Rear Axle Ratio
Click on
Rear Axle
Ratio and
change it to
5.9. Then
recalculate
performance.
You could
then repeat
this
sequence
trying
several
different
axle ratios.
Click on Rear Axle Ratio under General Vehicle Specs and type 5.9 over the current value of 6.2. (If 5.9
had not been within acceptable limits, the program will display the limits.) Then click on OK to return to
the Main Menu. There you can click on Running Conditions, then the Calculate Performance button at
this menu (as you did before) or just click on the Calculate Lap Times button at the top of the Main
Menu. The Calculate Lap Times button is a shortcut. Figure 4.8 shows the results: a Lap Time of 16.08
seconds with an average MPH of 84.0, with an "improvement" of .08 seconds
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Chapter 4 Examples
Figure 4.8 Test Results with 5.9 Axle Ratio
Improvement of .08 seconds by going to 5.9 ratio from 6.2 ratio.
Click
here to
show
Test
History
Log
options
.
An alternate way to see this comparison and improvement is to display the Test History Log. Click on
History as shown in Figure 4.8 and select Show History Now. You will get the screen of Figure 4.9 with
a history and comparison of the last 25 runs. (Although only 7 runs show, you can click and slide the
slide bar to see all 25.) The History Log is a convenient way to keep track of your results to watch
trends. We could use it here to find the best axle ratio.
Graph these results with the Baseline 6.2 axle results for the graph in Figure 4.10. Figure 4.10 points out
a couple of things:
• Engine RPM is lower throughout the run with the 5.9 axle ratio. This keeps the engine in a higher
HP RPM range for better acceleration and better performance. Figure 4.11 graphs acceleration Gs
for these 2 conditions, showing the 5.9 axle ratio shows higher acceleration for nearly the entire
time the vehicle is accelerating (power On).
• By clicking on a graph line with the mouse, you can bring up the cursor (vertical line). The value
of the Engine RPM lines at the cursor (near maximum RPM) is 7315 for the new 5.9 axle ratio and
7545 for the 6.2 axle ratio.
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Figure 4.9 Test Results with Test History Log
History Log
showing 2.0
and 3.08 axle
results and
“improvement”
Click and
move slide bar
to view all 25
of the last tests
Note showing
additional test
History Log
options.
Figure 4.10 Comparing Engine RPM
Click on Last to
show pre-vious
results
Click on the
graph line to
bring up the
cursor line.
Engine RPMs
at the cursor
are shown
here.
“Last” run
with 6.2
Axle Ratio
Current run
with 5.9 Axle
Ratio
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Figure 4.11 Acceleration Gs for the Two Axle Ratios
Click on Data_
to_Graph and
select Accel Gs for
this graph.
5.9 Ratio shows
higher
acceleration for
nearly the entire
time the vehicle is
accelerating.
High negative
acceleration
due to braking
is about same
for both tests.
Figure 4.12 Changing Test Name in History Log
Click on Test
Name in
History Log to
change the
name to
something
more
descriptive
than the
program’s
default name.
Enter name
nere, then
click OK.
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Click on Back to return to the Test Results screen, then click on History and Show History Now. A
useful feature of the History Log is the ability to change the Test Title in the first column to anything you
want. Click on the Test Title for the 5.9 axle ratio run, then answer No to the question “Retrieve the
specs which produced these results?”. You will be shown a test input box like that of Figure 4.12. (You
will find the ability to Retrieve specs which produces certain results in the History Log to also be a very
useful feature. Another useful feature is to click on History, then Clear History Log. This lets you erase
all the History rows, which is useful when you are starting on a new project.)
We could continue to try different axle ratios through “cut and try” to find the ratio giving the quickest
lap times. However the program has a built in feature to do this automatically. Click on Back at the top
of the Test Results screen. Then at the Main Screen, click on Find Best Gear Ratio. The program will
automatically try a wide range of axle ratios to see which gives the quickest lap times.
For these LATEMODL.355 specs, the program finds the 5.4 axle ratio is the quickest, and it asks you if it
should load in that ratio. Answer Yes, and you find that the new lap time is 16.04 seconds, .04 better
than 5.9 and .12 seconds better than 6.2. However at a different track, a different axle ratio would be best.
Figure 4.13 Finding Best Axle Ratio
Click here to have program
find quickest axle ratio for
current specs.
Program will
automatically
try several
different axle
ratios to find
the one
giving
quickest lap
times.
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Conclusions:
•
•
•
•
The Circle Track Analyzer allows you to easily maneuver between screens and menus with the click
on a mouse.
The program has several useful features like the Performance Summary and History Log to track you
changes, and the Notes and Graphs to understand and analyze your performance.
The Circle Track Analyzer allows you to simulate "real world" modifications by simply typing in
new specifications which simulate the hardware modification.
Like most other vehicle settings, there is no single "best" axle ratio for the LATEMODL.355. The
"best" ratio will change depending on other specs like Track Length and Banking.
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Chapter 4 Examples
Example 4.2 Calibrating Circle
Track Analyzer for Your Car
When using the Circle Track Analyzer to predict the effect of modifications on a certain vehicle, it is best
to first "calibrate" the program to match the vehicle's actual results. "Calibrate" means to fine tune an
instrument (the Circle Track Analyzer in this case) to improve its accuracy. Once the program is
calibrated, its predictions are more likely to match your vehicle's response to modifications.
We will calibrate the program for a Late Model with a 406 motor. The car runs 16 second laps at the
local low banked quarter mile track. Ideally you could just go to the Vehicle Library and find an exact
match for this car. However there probably is not an exact match for any car already in the library, so we
will have to build one by adjusting the specs for a car from the Vehicle Library.
You can start with a completely blank screen for all vehicle specs by clicking on File, then New at the
Main Screen. You can also blank out just the Engine, Front Suspension or Rear Suspension by clicking
on File, then New at their respective screens. However, for most beginners it is recommended you
always start with a example vehicle. This way, for specs you don’t know, there is already a spec entered
which may be close to matching your vehicle.
The LATEMODL.355 in the Vehicle Library would be a logical choice. (It actually doesn’t matter
which vehicle you start with. Once you have entered in the specs for your car, you will get the same lap
times even if you start with a Quarter Midget or Busch car. The advantage of starting with a car close to
your car is that its specs are more likely to be accurate for specs you don’t know. Click on LATEMODL
in the Vehicle Library, then click on Open to open it.
Now you will start to actually enter specs for your car.
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Figure 4.14 Engine Examples
Circle Track Analyzer
Chapter 4 Examples
Click on File, then Open Example Engine to load
in example actual dyno curves.
Click here to load
an Engine
Analyzer power
curve.
Click on Calculate
to estimate a
power curve from
only a couple of
simple inputs, like
cubic inches and
a general
description.
Click on engines
to obtain a
preview, where
you can tell by
the comments if
this engine may
be similar to your
engine.
Engine specs
Click on Engine specs at the Main Menu to display the current power specs for the Late Model’s 355
Chevy. You could enter the cubic inches, pick a clutch setup and type in a dyno curve for your engine.
However, you don’t know your engine’s power curve. Fortunately, there are several options for building
a power curve, which include:
• Use the current curve which came with the Late Model file. The engine comments show that this
is for a 355 Chevy, so this may not be the best choice.
• If you had a complete dyno curve, you could enter the dyno curve in the right hand section of this
screen. This is usually the most accurate method, however be sure the dyno curve covers a wide
RPM range. You may have to estimate and enter torque and HP at higher and lower RPMs than
was actually run on the dyno. For example, if your dyno run is from 4500 to 7000, estimate and
enter data at 3000, 3500, 4000 RPM and 7500 and 8000. This is especially important if you run
the engine on the track above or below the RPMs of the dyno curve. The program assumes power
drops off rapidly above and below the RPMs for which you have actually entered torque and HP.
• Pick an example power curve supplied be Performance Trends. This is done by clicking on File at
the top of the Engine screen, then selecting Open Example Engine. This is a good choice if there
is an example which matches your engine fairly closely.
• You could build a power curve in one of Performance Trends’ Windows Engine Analyzer
programs, then send it to the Circle Track Analyzer.
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•
Circle Track Analyzer
Chapter 4 Examples
You could Calculate a power curve based on some very simple inputs and engine descriptions.
This is usually the last resort, but can still give reasonable power curves.
We’ll choose to pick an example, so click on File, then Open Example Engine as shown in Figure 4.14.
In the list of example engines, click on ones that look promising. The program will give a Preview on the
right side or RPM range, peak HP, and comments which describe the engine. If you want, you can click
on the top engine, then use the down arrow key [↓] to go through the entire list and see the preview of
each engine.
The G-406-2BBL engine looks fairly close to your engine (the G standing for “good”). You estimated
your engine made about 375 HP and the example G-406-2BBL shows about 10 HP over that at 387.
This is a fairly close match. Either click on Open or double click on G-406-2BBL to use these specs of
an actual dyno curve for a 406 2BBL. Your engine specs will now look like Figure 4.15. Click on Back
at the upper left corner or somewhere outside this menu to close it and return to the Main Screen.
Figure 4.15 Engine Specs Menu for Example Engine G-406-2.BBL
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Chapter 4 Examples
Vehicle Specs
Click on Vehicle to open the Vehicle Specs menu shown in Figure 4.16. This is one screen where there
are no examples to open. That is because all these specs can vary so much between different cars and
different track rules. Go through each specs and enter a number for your car.
Figure 4.16 Vehicle Specs
General Vehicle Specs
Enter the vehicle weight with driver and fuel level you want to simulate.
Enter the weight %s if you know them. If you don’t know them, but do know the corner weights, click
on one of the Clc (calculate) buttons next to them. They will open up a Calculation menu shown in
Figure 4.17. Note that this menu will open up with the corner weights for the current car already entered.
You will have to type your weights over these weights. When all 4 of your corner weights have been
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entered, the menu will display the Weight %s for your car. Click on the Use Calc Value(s) button to load
in these Weight %s.
Figure 4.17 Corner Weights Calculation Menu
As menu is first opened with corner
weights for current car specs.
After you enter your car’s corner weights,
menu shows Weight %s for your car.
Click on Use Calc Value to use the calculated Weight %s.
If your corner weights add
up to a different weight
than already entered for
Vehicle Weight, you
would get the message in
Figure 4.18. For most
situations, you would
answer this question Yes.
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Figure 4.18 Question After Calculating Weight %s
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You don’t know your car’s Height of CG, so
leave in the current height. Wheelbase you
measure at 102 inches with a tape measure, the
same as the example LATEMODL.355. Rear
Axle Ratio you know is a quick change with a
4.88 ring and pinion and 47 tooth top gear and
34 tooth lower gear. Click on the Clc button by
Rear Axle Ratio to obtain the menu of Figure
4.19. Type in your information to obtain a
calculated 6.03 axle ratio, then click on Use Calc
Value to load 6.03 back into the Vehicle Specs
menu. For Rear Axle Type you click on the
combo boxes’ down arrow key to see your
choices. Of the choices choose Quick Change
(more losses) best matches your car. (You may
not have realized it before, but there is a
“downside” to a quick change rear axle. Quick
change rear axles have more HP losses in them
due to the additional gears.)
Chapter 4 Examples
Figure 4.19 Calculation Menu for
Quick Change Rear Axle Ratio
Aerodynamics
For the Aerodynamic specs, click on the Type
combo boxes’ down arrow key to see your
choices. There are many choices and you
choose Typ Late Model. Notice how the aerodynamic specs are now “grayed out” and you can’t change
them. That’s because your choice
Figure 4.20 Aerodynamic Type Choices
of Type is telling the program all
Click here to
it needs to know. To enable these
drop down list
specs so you can change them,
of choices
you would have to choose the top
choice in the Type list of Use
Click on
Specs Below.
these arrow
buttons to
see entire
list of
choices
Transmission
For the Transmission specs, click on the Type combo boxes’ down arrow key to see your choices. Std
Duty Manual seems reasonable so you choose it. For Ratio of Gear Used, enter 1 since you run your
trans in top gear with a 1:1 ratio.
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Rear Tires
Chapter 4 Examples
Figure 4.21 Calculation Menu to Help
Estimate Tire Traction Factor
For the Rear Tires specs, click on the Type combo
boxes’ down arrow key to see your choices.
Typical Racing Tire (average traction) seems the
closest match for your 10” tires. You’re not sure of
the Wheel & Tire weight, but the current setting of
40 seems about right, so you leave it 40. You enter
in your Left and Right rear tires’ circumferences of
87 and 89 and the program shows you the Stagger
of 2”. Enter in the Tread Width of 10”. Click on
the Clc button by Traction Factor to be shown the
Calculation Menu of Figure 4.21. Click on the
combo boxes’ down arrow key for your choices
and choose Average Suspension Setup.
Click on the Back button to return to the Main
Screen.
Front Suspension
Click on Front Suspension to open the Front Suspension Specs menu shown in Figure 4.23. You may
first be given an important notice, shown in Figure 4.22. The Circle Track Analyzer can not analyze all
details of handling and vehicle performance.
Figure 4.22 Tip on Limitations of Circle Track Analyzer
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Figure 4.23 Front Suspension Specs
Click on
File, then
Open
Example
Front
Suspensio
n for
possibly
finding a
suspension
layout
close to
your car’s
layout
Like Engine Specs, this screen does have examples to open. Click on File, then Open Example Front
Suspension as shown in Figure 4.23. In the list of example suspensions, click on ones that look
promising. The program will give a Preview on the right side of spring rates, camber, and comments
which describe the suspension. If you want, you can click on the top suspension, then use the down
arrow key [↓] to go through the entire list and see the preview of each suspension.
None of the Example suspensions appear to be closer to your suspension than the current
LATEMODL.FAB already part of the LATEMODL.355 vehicle. Therefore, you should measure your
front suspension as discussed in Example 4.3. You notice the spring rates and camber is different than
your car, so you type them in (600 and 550 for right and left springs, and -4 and 2 for right and left static
camber). Note that if the suspension’s layout is significantly different than your car’s, the effective
wheel rate could be much different for your car, even if you type in the correct spring rate. However,
for the other specs, you will leave these specs as the example vehicle had them. When you have more
time, you will measure up your front end.
Click on the Back menu item in the upper left corner or click on the [ X ] button in the upper right corner
to return to the Main Screen.
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Chapter 4 Examples
Rear Suspension
Click on Rear Suspension to open the Rear Suspension Specs menu shown in Figure 4.24. You may first
be given a similar important notice as in the Front Suspension menu shown in Figure 4.22. Again, the
Circle Track Analyzer can not analyze all details of handling and vehicle performance.
You go through these measurements and make changes to more closely match your car. You type in
your spring rates of 200 and 225 for the left and right. Note that if the suspension’s layout is
significantly different than your car’s, the effective wheel rate could be much different for your car,
even if you type in the correct spring rate. Rear suspension measurements are usually not a critical as
front suspension measurements. When you are finished, click on the Back menu item in the upper left
corner or click on the [ X ] button in the upper right corner to return to the Main Screen.
Figure 4.24 Rear Suspension Screen
Name of Rear Suspension File
Your choice
of Type will
significantly
change the
appearance
of this
screen and
what inputs
you are able
to enter.
General
Layout
drawing of
Rear
Suspension
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Chapter 4 Examples
Running Conditions
Click on Running Conditions to Weather
conditions, driver preferences and most
importantly, track specs. Since you are
not that interested in how weather
conditions affect performance, you
select Typ Nice 70 deg day in Midwest.
You will now notice that the other
weather specs are “grayed out” or
disabled. You think ”Good, now I don’t
have to worry about them.”
Figure 4.25 Selecting Simple Weather Specs
For the Reports/Graphs spec of Show
Results Every ... you leave it as is
(because you are not sure what it means). Basically, if you want more detailed results, suspension
analysis and graphs you will select a smaller time increment. This will be something you will use when
you are more familiar with the program.
For Track Specs you will select a Type from the list which most closely represents your track: Typ 1/4
Mile Low Banks. As with Weather Specs, the other
track specs are now disabled.
Figure 4.26 Simplified Track Specs
For Driver, you leave the existing
LATEMODL.355’s driver description of Typical
Aggressive Driver. The Running Conditions screen
should now look like Figure 4.27.
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Figure 4.27 Running Conditions for Your Car
Chapter 4 Examples
Notice how most
specs are
disabled (grayed
out) because
you chose
simple “Types”
for Track
Weather, Track
Specs and
Driver catagories
Click here to
calculate lap
time, or return
to Main Screen
and click on
Calculate Lap
Time button
there
Calculate Lap Time Performance
Whew, we’re finally done! Now for the fun stuff, lets see how this car performs. Click on the Calculate
Lap Times button in the Running Conditions menu, or click on the Back button to return to the Main
Screen, then click on the Calculate Lap Times button at the top of the Main Screen.
The program calculates a lap time of 14.04 seconds with a average MPH of 64.1 MPH. The results also
show the Mx and Mn (maximum and minimum) RPM during the run as 6537 and 3580. Your car
actually drops to a lower RPM in the corners, down to 3400 RPM and revs to 6300 before braking.
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Figure 4.28 Results for First Try
Circle Track Analyzer
Chapter 4 Examples
Click here for History Log shown below.
Summary
shows 14.04
seconds and
64.1 MPH,
faster than
your car’s
14.5 second
laps.
Highest and lowest RPMs (Mx and Mn
RPM) are shown in the History Log also
Lowest
RPM
(minimum
or Mn
RPM) is
shown as
the first
EngRPM
at the start
of Turn #2.
Mx RPM
would be
somewher
e down in
the
EngRPM
l
Match My Lap Times Feature
The program is currently predicting your car runs faster than your actual car’s 14.3 second laps. We
should fine tune these specs to get a better match between real lap times and what the program predicts.
In previous versions of Circle Track Analyzer, this would mean doing a lot of “cut and try”. Adjust a
spec, see if you got a better match on, say Mn RPM. If you did, now did you “screw up” your Lap Time,
etc.
The solution is the Match My Lap Times option, available at the Main Menu. Return to the Main Menu
from the Test Results screen of Figure 4.23. Click on the Match My Lap Times button at the top, to
display the menu similar to Figure 4.24. Enter in your actual performance, including a description of
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your engine. You choose ‘500 2BBL, ported heads’ as
the engine description. It should look like Figure 4.29.
Then click on the OK (adjust veh. specs to match
performance) button.
Chapter 4 Examples
Figure 4.29 Match Lap Times
The program makes several passes adjusting critical
specs between each pass, fine tuning the specs to find a
combination which best matches your actual vehicle’s
performance. After 30-40 passes, it arrives at the
combination shown in Figure 4.30. At the top of this
menu you see how close these new specs will make the
performance match. In the lower section, you see the
Old specs, and the new ones arrived at, which you can
either Keep, or discard and return to the old specs. You
see that the program adjusted tire Traction Factor down
to about 77% from 85%, and HP down slightly to 376
from 387. However, the program estimates that a 406
engine with a 500 2BBL and ported heads should make
421 ft lbs, more than the example power curve which had
394 ft lbs.
Click on the Keep These New Specs button to keep these
new specs.
Note: The combination of specs arrived at by the Match My Lap
Times feature are just one of possibly many combinations which
produce your car’s performance. They are NOT necessarily the
most accurate combination of specs to match your car.
The menu of Figures 4.29 and 4.30 are now gone. At the Main Menu, calculated performance and you
confirm these specs do give results as stated by the Match My Lap Times screens, and that do match your
car, just as shown in Figure 4.30.
Saving Your Car
Return to the Main Menu and click in the Vehicle Comments section and change them to match these
specs for your Late Model running 14.3 seconds. There are comments which can be entered for the total
vehicle at the Main Screen, and for the individual components of Engine, Front Suspension and Rear
Suspension. An easy way to show all these comments is to click on the Show All Comments button at
the Main Screen. Figure 4.31 shows what you could type in for comments.
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When finished, click on the Save
Vehicle button, or on File and then
Save Vehicle. You are first as shown
Figure 4.32. You answer No, since
these specs no longer represent the
LATEMODL.355, but that you want to
give it a new name. Next the screen
shown in Figure 4.33 is displayed.
Change the New Vehicle Name from
LATEMODL.355 to something that
matches these specs, like MYLATMO.DEL.
Circle Track Analyzer
Chapter 4 Examples
Figure 4.30 Results of Match Vet. Perf.
As Figure 4.31 shows, there are
individual File names for the Engine,
Front Suspension and Rear Suspension.
You should also go into each of these
menus and save these components
under a new file name, one the matches
the components on your car. If you do,
then you will want to update the
Vehicle file with these new component
names also. At the Main
Figure 4.31 Editing all Comments
Screen, click on File, then
Save to update MYLATMO.DEL with these new
component file names.
Now you are ready to check
various modifications on your
vehicle, like changing gear
ratios, tire size, or power
curves, etc.
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Conclusions:
•
•
•
Figure 4.32 First Screen for Saving Vehicle
After accurately entering
specs, and then fine tuning
them with the Match My
Lap Times feature, the
Circle Track Analyzer's
results can closely match
the results of most any
specific vehicle.
The program has several
options for entering specs,
like picking example specs
from preloaded examples, preloaded lists, or by calculating them using Calculation menus from
other known information or measurements
You can make most any file from the Vehicle Library match your vehicle's specs following this
procedure. Then you can save all these specs under a new name in the library for use at any
time in the future.
Figure 4.33 Screen for Entering New Vehicle Name for Saving
Click on File, then Save As or Save Vehicle button to save specs
Type in
most any
name, then
click OK.
The program
will tell you if
it must
change it to
be a valid file
name for the
computer, as
shown here.
Click here
to show
and edit all
comments,
Fig 4.xx.
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Chapter 4 Examples
Example 4.3 Analyzing the Front
Suspension
The Circle Track Analyzer has several ways for you to analyze your front suspension. The Front
Suspension input screen has several analysis features itself. Then once lap time performance has been
calculated, the Analyze Suspension option shows you what the suspension will be doing as the car goes
around a particular track.
Start this example by opening the BUSCH car from the Vehicle Library. Then go to the Front
Suspension screen as shown in Figure 4.34. You may notice a message appears which says the this
version of the program cannot accurately predict how suspension changes will affect lap times.
However, it can still estimate how suspension changes will affect weight transfer, roll, spring deflection,
front camber change and front roll center location.
Figure 4.34 Front Suspension Screen for 96-BUSCH.V-8
Click on
File, then
several
options are
available for
Opening
saved
suspension
file, printing
blank
worksheets,
etc for
entering
specs or
evaluating
other
suspension
setups.
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From this menu, you can:
• Enter or edit any of the measurements and specifications displayed, and watch calculated specs and
the layout drawing be updated automatically.
• Open or Save a file of complete front suspension measurements by clicking on the File menu item,
then either Open, Save or Save As.
• Add, edit or review comments to describe the front suspension measurements currently displayed.
• Produce various amounts of suspension Dive and Roll and watch Camber, Roll Center and Spring
Compression change. (You must be in the ‘Show Big’ mode to see Spring Compression.)
• Change the Options to somewhat customize this screen for you.
• Get Help to explain these options by clicking on Help or pressing <F1>. Help definitions are also
available anytime you click on an input spec’s name or input box or a calculated spec name or value.
See Figure 4.36.
• Return to the Main Screen by clicking on Back (or File, then Exit).
At the top of this screen, the blue title bar shows the current Front Suspension is [ 96-BUSCH.LOW ],
which is the front suspension for the Busch Series Thunderbird on a low banked track.
If you wanted to analyze a different front suspension, you could click on File in the upper left corner,
then select Open Example Front Suspension. See Figure 4.34. You will obtain a screen like Figure 4.35
of the Front Suspension Library, which lists files of suspension measurements which have been provided
by Performance Trends for your convenience. You could also click on File, then New to blank out all
measurements here to start with a clean “sheet of paper”.
Figure 4.35 Front Suspension Library
Files are arranged
alphabetically.
Click on a file to
highlight it and
display a Preview.
Then click on the
OK button (or
double click on file
name to Open in
one operation).
The Advanced
button opens up a
standard Windows
screen to let you
open files from
most any folder or
disk drive (not
available in
Beginner level).
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For now, lets just analyze the current Busch Tbird front suspension. If some measurement is not familiar
to you, click on its name or the spec and a brief description appears in the Help frame, along with a page
# from this manual for more help.
Figure 4.36 Specs for the File 96-BUSCH.LOW
Click on
most
any
specs
for a
brief
description to
be given
in the
Help
box at
the
bottom
of this
screen.
Changing Specs: Enter X&Ht Readings, Frame & Ball Joints Option
First, lets try changing a measurement. For example, lets raise the ball joint on the right upper control
arm 1/2 inch. This would mean the Right(Height) measurement for Upper Ball Joint (the distance from
the ground) would increase .5 inches. So change 20.4 to 20.9. When you get ready to press <enter> after
typing in 20.9, watch the drawing, especially the right side suspension at point A and Camber Gain.
(Remember, this is a front view, so the right side of the car is actually on the left side of the screen.)
Important: Always remember you are looking at a Front view of the car.
This means the Right side of the screen actually shows the Left side of the
car and the Left side of the screen shows the Right side of the car.
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Figure 4.37 Front Susp. Screen after Raising Rt Upper Ball Joint to 20.9 “
Table 4.1
Before
After
Upper Rt BJ Ht
Roll Center Ht
Roll Center Rt
Camber Gain
Stc Camber
Upper Arm Len
Upper Arm Ang
20.4
3.7
4.7
-.81
-2.5
7.16
24.78
20.9
4.0
7.2
-.99
-2.05
7.38
28.30
Figure 4.38 Front Suspension Options
Press <enter> and notice how Camber
gain changed from -.81 to -.99. See
Table 4.1. This minor change will
produce slightly more negative Camber
Gain, which means the right tire will see slightly more negative camber for the same amount of Dive in
the corner or during braking. You will notice that Stc (static) Camber (in the Other Specs at the right
side of the screen) changed from -2.5 to -2.05 degrees.
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You will also notice that the Length
and Angle of the Upper Arm
(printed in light gray in the lower
left corner changed from 7.16
inches to 7.38 and 24.78 degrees to
23.30. You might be thinking that
the only way for the length of the
arm to change is by installing a
different arm, which is correct.
What we simulated was raising the
Upper Ball Joint and adjusting the
length and angle of the upper arm so
the Frame Pivot would stay in the
same spot.
Circle Track Analyzer
Chapter 4 Examples
Figure 4.39 Notice when Changing Options
If you want to change the height of
the Rt Upper Ball Joint, but use the
same arm (arm length stays the same), you can start adjusting the Rt Upper Ball Joint X dimension until
you get back the original length of 7.16 inches. For example, after a few tries, you’d find that an Upper
Ball Joint X of 21.25 inches would produce a length of 7.16 inches.
If you click on Options at the top of the Main Screen you will see that the first option (Enter X&Ht
Readings, Frame & Ball Joints) is checked. This means you enter the X and Height readings of both
ends of the arms, and the length is calculated from those readings. If you select its alternate option (Enter
X&Ht at 1 End, Arm Len & Angle), then you could change the Height at the Upper Ball Joint and the
mount at the frame would change as necessary to hold the length of the arm and its angle constant. You
could then change the Angle of the arm to produce most any X or Height at the Frame Mount.
Changing Specs: Enter X&Ht at 1 End, Arm Len & Angle Option
Lets try this. Click somewhere outside the menu choices of Figure 1.5 to close these choices without
changing them. Then click on the 20.9 and type in 20.4 and press <enter> to return it to its original
value. Camber Gain should go back to -.81 and Stc (static) Camber should go back to -2.5.
Now click on Options and then on the Enter X&Ht at 1 End, Arm Len & Angle option. You will be given
the notice shown in Figure 1.6 and see that the Upper and Lower Arm Dim. (“Dim.” is an abbreviation
for “dimensions”) are now enabled so you can enter them directly. The Upper Frame Mount and Lower
Ball Joint inputs are disabled (printed in light gray), meaning these values will be calculated from the
other inputs. You may notice that the Height of the Lower Ball Joint change slightly, from 8.75 to 8.74
which is due to slightly rounding differences in the math. This hundredth inch difference will not produce
any significant error in the results. See Figure 4.40.
Now change the Upper Ball Joint Height from 20.4 to 20.9 and press <enter>. Notice how the Length of
the arm stays at 7.16 inches and the Angle stays at 24.78 degrees. Frame Pivot X and Height have
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Chapter 4 Examples
Figure 4.40 Changing Upper Ball Joint Height with the Enter X&Ht at 1 End,
Arm Len & Angle Option Selected
changed as they would in order to keep the length and angle constant. Stc Camber changes just as it did
before to -2.04 because the Ball Joint has moved the same as before. However the Camber Gain now is
-.77 because the arm angle stayed at 24.78 where the arm angle changed to 28.30 after raising the Ball
Joint Height to 20.5.
The choice of which of these options you use (Enter X&Ht Readings, Frame &
Ball Joints or Enter X&Ht at 1 End, Arm Len & Angle) can have a significant
effect on how your inputs affect other specs. Use the one which makes the
most sense for the type of modification you are trying to simulate.
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Chapter 4 Examples
Show Dive & Roll
This screen lets you simulate the car going through various amounts of dive and roll. To see this feature,
click on the Yes option for Show Dive and Roll. You will see the Dive and Roll text and arrow boxes
become enabled so you can enter a certain amount of vehicle Dive in inches and Roll in degrees. The
arrow boxes let you increment Dive and Roll up and down by clicking on the appropriate arrow. You
will also see the suspension drawing move just as it would in the real vehicle. The suspension in the
static position is drawn in light gray for comparison (or dark gray if you have chosen that Option). The
static Instant Centers and Roll Center are also drawn in light gray so you can see how much they have
moved due to Dive and Roll.
To the right of the drawing, you will see Dyn Camber also change as you go through various amounts of
Dive and Roll.
Figure 4.41 Analyzing the Suspension Motion with Dive and Roll
Dynamic suspension is shown in Black, Blue and Red.
Static suspension is shown in gray for comparison.
Dynamic
Camber
shows
how tire
camber
changes
with Dive
& Roll.
Click here
to show
more
detail, like
Figure
4.42
Car is shown diving and rolling to the right
(positive Roll), which is what the car
would do braking into a left hand turn.
Click on
arrow
buttons to
increment
Dive & Roll
up or
down, or
just type in
your
desired
Dive & Roll
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Dyn Camber, deg: Dynamic Camber is the camber the tire will see due to Dive and/or Roll.
Camber has a large impact on the tire patch on the track, and therefore tire traction. By optimizing
camber you can produce higher traction in the turns and therefore faster lap times.
Figure 4.42 Screen of Figure 4.42 ‘Drawn Big’
Spring
Compressio
n is only
displayed on
the Front
Suspension
screen in
Draw Big
Mode
Click here to
return to
original
screen.
Tips for understanding Roll Center, Camber and Camber Gain
discussed above are listed at the end of Appendix 2.
Another option at this screen is the “Draw Big” button next to the Dive and Roll inputs. Click on this
button to draw the suspension layout larger as shown in Figure 4.42. Again the Dive and Roll inputs are
available, but now you may see some details better. The Draw Big screen has a calculation which is not
available on the normal screen, called Spring Compression:
Spring Compressn: Positive spring compression means the spring is compressed from its
static (standing still before any Dive or Roll) position, or the car is diving. Negative spring
compression means the spring is elongated or the car is rising. By making spring compression match
the motion shown by your shock travel indicators, you ensure you are moving the suspension through
somewhat the same motion which your car sees on the track.
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Analyze Suspension
Circle Track Analyzer
Figure 4.43
Chapter 4 Examples
Click here to Analyze Suspension
as shown in Figure 4.44
You can also analyze the suspension
actually going around a particular
track. Change the Upper Ball Joint
Height back to the original 20.4
inches. Then click on Back to return
to the Main Screen. Then calculate
lap times. At the top of the Test
Results screen, click on Analyzer
Suspension as shown in Figure 4.43.
This will produce the screen shown in Figure 4.44.
Fig. 4.44 Suspension Analysis Screen (See Section 3.6, page 116 for details)
Unlike the Front Suspension Screen where you enter
your “guess” at Dive and Roll, Dive and Roll are
calculated from track specs and vehicle specs.
Track Position and
other info shown here
Spring compression and tire load
on all 4 corners shown here
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Before entering the Suspension
Analysis Screen, you may get a
notice like Figure 4.45. The
Analysis Screen lets you compare the
suspension of the current test results
with some previous test results you
have saved as a baseline. However,
this comparison is only possible if
the previous test was run on the same
type of track (same Track Length and
Infield Width, but Banking can be
different).
Circle Track Analyzer
Chapter 4 Examples
Figure 4.45 Possible Baseline Notice when
Entering Suspension Analysis Screen
One important feature of Figure 4.44 is watching the Front Suspension go through “computer predicted”
Dive and Roll and watching Camber and Roll Center Location of the Front Suspension change. This
avoids you having to “guess” at reasonable combinations of Dive and Roll to enter in the Front
Suspension screen.
Figure 4.46 Baseline Question Asked when Exiting
The Suspension Analysis screen
Suspension Analysis Screen
displays lots of information and
has several options. Read
Section 3.6 (starting on page
116) to understand all the
possibilities. For now, click on
the [X] box in the upper right
corner, or the [-] box in the upper
left corner to close this screen.
The program will ask you if you want to save these results as a Baseline. Answer Yes because we will
compare this setup to the one where we raised the
Figure 4.47 Entering Baseline Title
Right Upper Ball Joint .5 inches. See Figure 4.46.
The program will take some times while it saves these
results, then it asks you for a name for these results.
Enter something meaningful, as shown in Figure 4.47.
Click on Back at the Test Results screen to return to
the Main Screen. Click on Front Suspension and
change the Right Upper Ball Joint Height from 20.4 to
20.9 as we investigated before. Then calculate Lap
Times and click on Suspension Analysis. You may
not automatically get the Baseline results shown with
the new results. If not, click on Options and then
Show Baseline.
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Figure 4.48 Suspension Analysis Comparing Change to Baseline
Click on Options, then Show Baseline to compare saved Baseline to current results
Note that Roll and Dive have increased, primarily because wheel rate dropped
with new Upper Ball Joint Ht (even though roll center increased slightly)
Right spring compression has increased due to drop in wheel rate
Baseline results from previous run (20.4” Upper Ball Joint Ht) for
comparison. On computer screen, these Baseline results are
shown in bright pink for easy identification.
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Conclusions:
The Circle Track Analyzer has several features to analyze suspension effects, especially the front
suspension which is usually the most critical.
• The Front Suspension input screen has several features itself to analyze camber and roll center
changes.
• After Lap Times have been calculated, the Analyze Suspension screen shoes what the
suspension is likely to do actually traveling around a track of a particular design.
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Appendix 1: Accuracy and
Assumptions
Background:
The Circle Track Analyzer was developed as a:
• Tool to help predict effects of certain engine and vehicle modifications for engine builders,
racers, and performance enthusiasts.
• "Theoretical Race Track" to allow anyone to try things which are too expensive, difficult,
dangerous, or impossible with a real vehicle.
• Learning aid for those who want to better understand vehicle dynamics during full power
acceleration.
The Circle Track Analyzer will provide you an engineering estimate of what should occur when general
modifications are made based on the principles of vehicle dynamics and physics. By seeing all the
specifications which go into the calculated results, you may have a false sense that the computer knows
your vehicle exactly; what manufacturer's tires you are using, who built the chassis, what your 4 link
settings are, etc. Actually the computer does not know if the specifications are for a production Yugo or
a Earnhardt’s #3 car.
A good analogy to the Circle Track Analyzer is a cylinder head flow bench. A flow bench can not
predict exact torque and HP curves, but is still a vital tool for engine development. In the same way, use
the Circle Track Analyzer results as a guide or second opinion of how your vehicle should perform under
near optimum conditions.
Iterations
Before we talk about accuracy, it is important for you to understand the types of calculations going on
inside the Circle Track Analyzer and other sophisticated simulation programs. A simple program could
involve calculating top speed from HP and frontal area:
1/3
Top Speed
=
K1 x Frontal Area x HP
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You enter an engine HP and a Frontal Area and obtain a Top Speed value. The answer you obtain on the
left side of the equation has no effect on the inputs on the right side of the equation.
However, lets look at a simplified version of the equation which the Circle Track Analyzer uses just to
calculate the maximum potential tractive force (traction) the tires can produce to accelerate the car
forward.
Max Tractive Force = Tire Friction x ( Wt on Rear Tires + Wt Transfer )
Where: Wt Transfer depends on the vehicle's acceleration rate which
depends on the tires Max Tractive Force.
In this case the "Max Tractive Force" answer you get on the left side has an effect on the inputs to the
equation on the right. The only way to solve equations like this is through "iterations". Iteration is a
process where you assume an answer, use that answer in the right side of the equation, calculate the
actual answer and see if the actual answer is "close enough" to the answer you assumed.
Iteration Process:
(For this example we will not use actual numbers since the calculations are quite complex)
Assume Max Tractive Force is 3000 lbs
Calculate that the vehicle acceleration could be .8 Gs and the Wt Transfer value is 600 lbs
Using the Wt Transfer of 600 lbs, we now calculate that the Max Tractive Force is 3200 lbs
Are assumed Max Tractive Force and calculated Max Tractive Force "close enough" (within
20 pounds)
No, so do again using new Max Tractive Force answer
Calculate that the vehicle acceleration could be .85 Gs and the Wt Transfer value is 640 lbs
Using the Wt Transfer of 640 lbs, we now calculate that the Max Tractive Force is 3218 lbs
Are assumed Max Tractive Force and calculated Max Tractive Force "close enough" (within
20 pounds)
Yes, so an approximate answer is: Max Tractive Force = 3218 lbs
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If "close enough" was 200 lbs, our first answer of 3200 lbs would have been good enough. If "close
enough" was 1 lb, it may require many more calculations to arrive at an answer which is "close enough".
If the equation is very complex and the inputs are an unusual combination, no answer may be reached no
matter how many times the calculation is performed. This is called "not converging on a solution".
Making the tolerance ("close enough") small will produce more exact answers but will require more
calculation time. Performance Trends has selected tolerance bands for iterations which give good
accuracy with reasonable calculation times, and allow the process to "converge on a solution".
Because many of the equations within the Circle Track Analyzer must be solved by iterations, there is no
one exact answer. All calculations are an approximation. Therefore, do not be alarmed if a Lap Time
improvement of .02 seconds is shown for changing in Dew Point from 67 to 66, but changing from 66 to
65 showed a .00 second improvement. These results are basically saying lowering the Dew Point results
in a very small gain in Lap Time.
Major Assumptions
To make the Circle Track Analyzer and the specifications which describe the vehicle containable on a
personal computer, several simplifying assumptions are made which are listed below. Other
approximations and assumptions exist as identified in Section 1.3 A Word of Caution and scattered
throughout this manual. Also see Assumptions in the Index.
•
•
•
•
•
•
•
•
•
•
•
•
All vehicle components are assumed to be perfectly stiff, which means that suspension members
do not bend, tires do not deflect (squat or shift), suspension bushings do not deform or move.
All tires behave about the same as far as how cornering ability changes with load on the tires.
Actual tires vary greatly between designs.
Tires can continually handle all the heat buildup caused by pushing them to their limits.
Maximum cornering traction occurs when all 4 tires are evenly loaded.
There is no delay in engine torque getting to the tires due to driveshaft, axle or tire "wrap up".
There are no shock absorber effects.
There are no bumps or roughness in the track.
If spring compression as shown in the Suspension Analysis screen in Section 3.6 exceeds 1.5
inches, additional spring stiffness is added to somewhat simulate the springs coils touching, and to
avoid the suspension encountering some impossible situations.
Tire camber and camber changes are not used to estimate tire traction and cornering ability at
different parts of the track.
Steering inputs and therefore tire slip angle are not used to estimate tire traction and cornering
ability at different parts of the track.
The brakes are assumed to be large enough and capable of dissipating all heat to be able to
continually brake at levels capable of the tire’s maximum traction.
In this version, Roll Center Offset from car centerline (left or right) is not used to predict lap times,
traction, corner weights, or suspension motion. Most text books and authorities do not address the
effect of Roll Center Offset, but all discuss how Roll Center Height affects vehicle roll.
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•
Circle Track Analyzer
Appendices
There is no change in the Height of CG due to "pitch rotation" or the body lifting or squatting.
Accuracy
From reading the assumptions above and scattered throughout this manual, it is obvious several important
aspects of vehicle performance are "glossed over". Therefore, it is impossible to make exact predictions
of what will happen to your vehicle when modifications are made.
There are many combinations of vehicle specs which can produce the same lap times (and even the same
maximum and minimum engine RPMs). Therefore, do not assume that if you have gotten the lap times
to match your car that now you have your car simulated correctly. Also, especially do not assume that
you now have the program simulating your suspension motion correctly.
This program should be used as a guide to help you
visualize what can happen on your car when you make
general (not detailed) modifications. In no way does
it exactly simulate your car on a particular track, or can
it predict exact changes in handling.
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Appendices
Appendix 2: "General Tips"
The following "tips" will show you how to change the Circle Track Analyzer calculations by adjusting
various inputs.
Calibrating "Tips"
Calibration is the process of adjusting the program's inputs to produce results which closely match a
certain vehicle's drag strip results. Example 4.2 shows this process in some detail, including the Match
My Lap Times feature. Here are some tips on how to adjust vehicle specs to get the computer’s predicted
lap times to match your lap times if the Match My Lap Times feature cannot come up with a good
solution.
Obviously, many inputs affect lap times. Here are the ones which are difficult to measure or know for
certain, and have a large effect on lap times.
To Decrease Lap Times (faster laps)
•
•
•
•
•
•
•
•
•
More Engine Power (especially long tracks)
Higher Banking
Wider Infield Width
Higher Traction Tire ‘Type’
Higher Tire Traction Factor
Higher Driver Aggressiveness (Braking and/or Accelerating)
Lower Lift Coefficient (larger negative numbers, especially big tracks)
Lower Drag Coefficient (especially long tracks)
Lower Frontal Area (especially long tracks)
Using Dynamometer Data for Engine Power Curve Specs
Engine Power Curve specs are discussed in Section 2.2. Dynamometer tests which measure engine
performance can be done in different ways. How the test is done can over-estimate or under-estimate the
engine's torque and HP in the vehicle.
The Circle Track Analyzer works best if you enter steady state dynamometer results, with the engine
equipped exactly as it will be in the vehicle. "Equipped" means with the full exhaust and intake system,
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Appendices
all accessories running like water pump, fan, etc. "Steady state" means that engine RPM is stable (not
changing) when the torque and HP are measured. This is sometimes called a “step text”.
Accelerating dynamometer tests, where the engine speed is constantly increasing (i.e. 300 RPM/sec), can
under-estimate an engine's steady state performance. You may think an accelerating test best represents
an engine accelerating in a vehicle. However, the Circle Track Analyzer calculates the power loss due to
accelerating the engine, which changes with gear ratios, track specs, etc. See "Inertia" discussion below.
Rotating Inertia
The difference between stationary and rotating mass is important for a racer to understand. Ever racer
knows that the less a car weighs, the faster it can accelerate. However, not every racer knows that
removing 30 lbs from the vehicle's rotating components (wheels, tires, engine flywheel) will show a
larger improvement in accelerating performance than removing 30 lbs from the frame or body.
This is because not only do you have to accelerate the tires down the quarter mile, you have to get the
tires to spin faster also. The spare tire in the trunk is easier to accelerate than the same tire mounted on
the axle. The tire on the axle has both mass and rotational inertia.
Rotational inertia is a part's resistance to changing its rotational speed. Jack up the axle and try to spin
the wheel. Neglecting friction, a heavier wheel requires more force to spin than a light wheel. In
addition, if the mass is concentrated in the tire and less in the wheel, it will require even more force to
spin. That is because rotational inertia depends on mass and the distance the mass is from the center of
rotation. See Figure A1.
For this reason,
rotating components
with small
diameters, which
concentrate the
mass close to the
center of rotation,
have much less
inertia. These
components consist
of the driveshaft,
axle shafts, etc.
Reducing the
weight of these
components
insignificantly
reduces you rotating
inertia Rotating
components with
170
Figure A1 Changing Rotation Inertia
Base Inertia
Reduce weight 50%
Same Diameter
Inertia is reduced 50%
Requires only half the HP
to accelerate
Reduce Diameter 50%
Same Weight
Inertia is reduced 75%
Requires only a quarter
the HP to accelerate
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Circle Track Analyzer
Appendices
larger diameters (flywheel or torque converter, wheels/tires, somewhat in the crankshaft, damper and
transmission components) contain most of the vehicle's rotating inertia. These are the components to
concentrate on when trying to reduce rotating inertia. For example, removing 1 pound from the
engine’s flywheel will have 100 up to 1000 times or more effect on the vehicle’s rotational inertia than
removing 1 pound from an axle shaft.
Example
Try some examples with the Circle Track Analyzer with the 96-BUSCH.V-8. The Baseline 96BUSCH.V-8 performance is a 19.36 seconds lap time.
Now, remove 32 lbs from the Rear Wheels by setting Rear Wheels/Tires Wt = 10 instead of 42 in the
Vehicle Specs menu. (The program assumes the front wheels/tires weight the same as the rear.) This
modification simulates moving 32 lbs from the all 4 wheels and placing it somewhere on the body, since
we did not also reduce Vehicle Weight 128 lbs (4 x 32). Calculate performance an we get a new Lap
Time of 19.32 seconds. Nearly a four hundredths (.04) improvement just by moving weight around on
the vehicle (not moving it to change traction).
Engine Inertia
Engine inertia is more complicated than other rotating inertia on the vehicle. However, for cars which do
not shift or do not start from a stand still (circle track racing in 1 gear only), it is almost always best to
reduce engine inertia to improve acceleration.
The Circle Track Analyzer estimates the rotational inertia of the engine and clutch/flywheel or converter
and transmission parts based on:
• Displacement in the Engine Specs menu (the higher the displacement, the higher the inertia).
• Clutch Description in the Engine Specs menu.
Tips on Simulating Modifications
The previous "inertia" examples point out an error most users will make. When you make a
modification, always think of how it could affect each specification. The example of removing 32 lbs
from the wheels and tires not only affected Wheels/Tires Wt, but also Vehicle Weight and possibly the
Weight %s, Rear, Left or Cross. Below is a list of common modifications and the specs they may affect.
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Appendices
Engine Modifications
Engine modifications can change all Engine Power Curve specs and Displacement. If the engine is
naturally aspirated (not supercharged, turbocharged or uses nitrous oxide) and you increase the HP,
generally the RPM where the HP will peak will increase also. Vehicle Weight and % Wt on Rear Tires
may also change if you change to aluminum components (less weight) or add a supercharger (more
weight), etc.
Adding, Removing or Shifting Weight
•
•
•
Vehicle Weight
Weight %s, Rear, Left and Cross
Front & Rear Wheels/Tires Weight
Changing vehicle height
•
•
•
Height of CG
Suspension Specs, like heights o f Frame Mounts, Ball Joints, etc
Frontal Area, sq ft
Changing wheels and tires
•
•
•
•
•
172
All the Wheels/Tires Specs
Vehicle Weight, lbs
Weight %s, Rear, Left and Cross
Suspension Specs, like heights o f Frame Mounts, Ball Joints, etc
Frontal Area, sq ft
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Roll Center:
Several authorities agree that the static Roll Center (before any Dive or Roll) should be from 2.5" to 4.5"
above the ground. For road race cars (turning both left and right) you want to keep the Roll Center near
the car's centerline (left or right).
The farther the Roll Center is to the Left, the quicker the car will react (more it will Roll) when going
into a Left turn. For this reason, many asphalt circle track (left turning) cars locate the Roll Center to the
right of center (less Roll) and dirt cars locate the Roll Center to the Left of center (more Roll and
hopefully better "bite" at the right front). However, the car is more predictable "all around" if the Roll
Center is kept close to the car's centerline.
Higher banking (20 degrees or more) usually requires a lower Roll Center, in the 2-3 inch range.
The more mass in the front of the car (heavier engine or engine more forward), the higher the Roll Center
should be.
Some authorities believe a lower Roll Center works better on dirt because the higher body roll produces
more "side bite" from the tires.
Lower Roll Centers require stiffer springs to control Roll. However, stiff springs hurt traction on bumpy
tracks.
The less the Roll Center moves during Dive and Roll, the more predictable the car's handling.
Most authorities agree that holding the Roll Center position as constant as practical during Dive and Roll
is optimum.
Camber/Camber Gain:
For Circle Track cars (turning left), reasonable Static Camber values (before any Dive or Roll) are: Left
Side +1 to +2 degrees, Right Side -2 to -4 degrees, the tighter the turn, the higher the camber.
Wider and/or stiffer sidewall tires require less Static Camber.
Camber Gain should be in the range of -1.75 for a flat track, -1.25 for a medium banked track (10-15
degrees) and down to -1 for highly banked tracks (over 25 degrees) on the outside tire (right tire in a left
turn). For circle track cars (always turning left), the desired camber gain on the left side may be less or
even a positive number, depending on track banking and other factors. These Camber Gains are based on
the program's standard definition as the amount of Camber Change from 1" of Dive.
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Appendix 3: New Features in
Version 3.2
Here is a brief listing of some of the features new in Version 3.2:
174
•
Program is now a 32 bit version, fully compatible with newer operating systems, starting with
Windows, 95, then 98, Me, XP, and 2000. This also allows you to use much longer, more
descriptive file names for saving vehicles, suspensions and engines. It is also more compatible
with newer printers.
•
The program is now designed for 600 x 800 or higher resolution screens.
•
There is now an option in the Analyze Suspension screen to output an ASCII file of the wheel
loads for analysis in other programs.
•
The graph screen is now larger, and generally fills the entire screen.
•
Version 3.2 adds a major feature where you can estimate the change in corner weights and ride
height by jacking (turning adjusting screws) on the springs on the 4 corners.
•
The program now figures the wheel rates more like our more detailed Suspension Analyzer.
•
This change in general stiffens up (increases) the wheel rates. It also makes the dive and roll
predicted in the Analyze Suspension screen more accurate. Some users reported that the
vehicle’s were “bottoming out” in the Analyze Suspension screen on high backed tracks with
lower spring rates.
•
Braking is now done more gradually, like a human driver, on high speed tracks.
•
The Front Suspension screen now has Edit options to copy measurements from one side to
•
another, and move all measurements in, out, left right, up, down, or re-center all measurements
based on changes to the tire track.
•
The Front and Rear Suspension screens now accept fractions as inputs and convert the fractions
to decimal equivalents. For example, enter 8 5/8 and press <Enter> and the program will convert
it to 8.625. There must be a space between the whole number part and the fraction and you must
use a slash “/” in the fraction.
•
There is now a separate “Examples” folder for example vehicle files provided by Performance
Trends. New vehicles which you save will be saved to a separate folder.
•
File commands to save a vehicle file to a floppy disk, or open a vehicle file from a floppy disk.
•
The Rear Suspension screen now reports wheel rates for both bump (as before) and roll.
•
A preference has been added to allow you to tell the program to assume the rear axle is a Solid
Axle. This setting is then used to better estimate the effect of the engine’s torque on wheel loads
(lifting the right rear tire) in the Analyze Suspension screen.
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•
You can now choose to list vehicle, engine, front suspension and rear suspension files
alphabetically (as normally done) or by saved date, with the most recently saved files listed first.
This should make it easier to find recent files more quickly.
•
New Example Vehicles have been added, like Legends cars.
•
The user’s manual is now available from inside the program by clicking on Help at the top of
the main screen, then Display User’s Manual. The manual is in a high quality PDF format
•
The Performance Trends website is now available from inside the program by clicking on Help
at the top of the main screen, then Performance Trends on the Web.
Figure A2 New Options at Main Screen
Example Vehicles are now stored
separately from vehicles you create.
Corner Jacking
brings up screen
of Figure A3
Demo program can now be easily unlocked from Main Screen.
Windows Printer Setup now available from Main
Commands to Open From and Save To floppy drive makes it easy to transfer
vehicle files from one computer to another.
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Figure A3 Click on Corner Jacking Button at Upper Right of Main Screen for This Screen
Jack on any or all springs at once by typing in the
amounts of turns up or down, or click on the Up/Down
button to increment one turn at a time.
Watch the corner weights change
on all corners and see how much
the ride height will change.
See how much diagonal (cross weight) you
are dialing into or out of the car.
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Figure A4 Analyze Suspension Screen Results
The “baseline” condition here is
the Preference for “Independent
Rear Suspension”, with the New
condition being a solid axle.
Notice how the right rear shows
about 30 pounds less load when
accelerating with Solid Axle.
With the more accurate, stiffer wheel
rates, this vehicle shows only 2.6
inches of dive. With old Version 2.0’s
lower wheel rates, this vehicle would
show almost 4 inches of dive.
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Figure A5 List Vehicle Files by Date Last Changed in Open File Screen
Note longer, more descriptive file names.
New Option to List Files by Date Last Changed, which lists the files
you most recently worked with first.
Figure A6 New Help Options
178
New Help
Options
available by
clicking on
Help at top of
Main Screen.
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Appendix 4: New Features in
Version 3.5
Here is a brief listing of some of the features added since v3.2 was released. Some we added to later
versions of v3.2 and some are new in Version 3.5:
•
A major new feature is the concept of balancing the Front Lateral Load Distribution (FLLD)
with the rear lateral load distribution. This concept can be used to find a “balanced” setup by
adjusting spring and roll bar rates, and roll center heights. This is discussed in detail below.
•
The ‘Rule of Thumb’ Suggestions for a good starting point for a setup now includes a
suggestion for the rear roll center height. This is based on obtaining a recommended FLLD.
See details below.
•
The program can now do an angled, symmetric 4 link rear suspension, as used in the late model
Mustangs and GM Metric chassis.
•
Added the ability to do Camber Change and Roll Center Migration tables and graphs in the
Front Suspension Screen.
•
The Front Suspension Screen now calculates and displays 2 additional suspension
characteristics: 1) Tire track change (tire scrub) as the front suspension goes through dive and
roll. 2) Swing Arm lengths, the length from the tire center to its instant center.
•
Changed the name of the Corner Jacking button at top right of main screen to Corner Weights.
That’s because 2 new options have been added, letting you do Tire Diameter/Circumference
changes and weight/ballast movement to check the affect on corner weights
•
Screen colors are now more compatible with Windows XP.
•
Added ability to save a vehicle file to or open a vehicle file from a floppy disk or CD, with a
default drive letter from A to Z, selectable in Preferences.
•
New Example files have been added, like GM Metric 4 Link Rear Suspension..
•
Added 'Edit' options to the 'Calculate' menu item in the Engine Specs screen. The new Edit
options let you factor the power curves up or down, or re-sort the table if there are blank rows or
RPM increments out of order.
FLLD (Front Lateral Load Distribution)
When a car makes a turn, weight is transferred from the inside tires to the outside tires. However, how
this weight transfer is split between the front and rear has a huge impact on the feel and handling of the
car. If more weight transfer occurs on the front of the car, the outside front tire is being “overworked”
more than the rear outside tire, causing less cornering traction at the front. This is more likely to produce
understeer or a push. Very simplistically, if the Front Lateral Load Distribution is 50%, that means the
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weight transfer split between front and rear is the same, and that should produce neutral handling. The
book “Race Car Vehicle Dynamics” by Milliken and Milliken (with assistance by Terry Satchell)
discusses this concept in detail. This concept is similar to the idea of balancing the front and rear roll
angles presented in recent magazine articles.
Figure A7 shows the program displaying the FLLD for the current vehicle (currently 43.4%, which
would tend to oversteer) during the transition between releasing the brakes and going to the throttle, at
the apex of the turn (transistion between braking and power). During braking and under acceleration, the
weight transfer is much more complicated, and the FLLD concept can not be as easily applied.
Figure A7 New Options at Main Screen
Corner Jacking brings up screen of Figure A10
FLLD value for this car is shown
here, with a description of what it
means. Click on details for more
info on this tuning parameter,
including more complete vehicle
calculations.
Find button brings up screen of Figure A8, to let you
quickly find combinations producing different FLLDs.
Figure A8 is displayed if you click on the “Find” button shown in Figure A7. This “Find FLLD” screen
lets you find a certain Front Lateral Load Distribution (FLLD), which can be a good indication of how
the car will handle at the apex or transistion of the turn (no power, no braking).
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Pick the 'Adjust' factor to
tell the program what
vehicle component(s) you
want to adjust. Enter your
desired 'For This FLLD',
then click on the 'Find
Now' button. For perfect
theoretical 'Balance', the
FLLD should be 50%.
However, from
experience, Milliken
suggests a target 'starting
point' FLLD value of 5
percentage points higher
than the percent weight on
the front tires (100% Rear Wt % = Front Wt %).
By default, the program
will load in this value, but
you can change it to
anything else you want.
Higher FLLDs tend to
make the car tighter, with
more understeer. Lower
FLLDs tend to make the
car looser, with more
oversteer.
There are several ways to
obtain a certain Front
Lateral Load Distrbution
percentage.
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Figure A8 Find Front Lateral Load Distribution
Screen obtained by clicking on Find button in Fig A7.
3) Click here
to have
program find
new settings.
1) Pick what
to Adjust.
2) Select the
FLLD you
want. The
program will
default to a
typical value
based on your
car’s weight
distribution.
4) Click here to
have program
save these new
settings.
The new settings you find using this feature MAY NOT BE THE BEST AND COULD BE
UNSAFE. USE YOUR JUDGEMENT when making adjustments based on this concept.
To reduce the possibility of using very strange settings, the program will calculate the average front and
rear natural frequencies for the springs. If these frequencies are significantly different than those
typically used, the program will warn you. Typically, the front natural frequency will be in the range of
1.4 to 2.0 and the rear will be .1 to .5 points lower than the front.
For many vehicle combinations, the program can not find settings to match your requirements. Many
times this is due to the Front or especially the Rear roll centers being too high. High roll centers transfer
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more weight laterally through the suspension linkages and less through the springs, making the springs
and roll bar have less effect on this tuning factor. You may then want to have the program adjust the
Rear Roll Center to find the FLLD you desire. After you adjust the Rear Roll Center and keep this
change (click on OK/Keep), then you can go back into this screen and try adjusting springs and/or roll
bar and they are likely to have more affect.
Fig A9 Other Features using the FLLD Concept
At the top of the Analyze
Suspension screen, these
3 reports are all improved
using the FLLD concept.
If you find settings which you want to keep, click on OK/Keep and they will be loaded back to the
vehicle specs screen. For the Front and Rear Roll Center Heights for some suspension types, you must
make a mental note of this setting and go back into the Front or Rear Suspension Screen and try various
setting to arrive at this height. The program can not make this change automatically for you.
Figure A9 shows 2 reports which now also include references and suggestions based on balancing the
FLLD.
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Corner Weights
Figure A10 Corner Weight Screen from Clicking On Button in Fig A7
Two New Options in Version 3.5
The screen in Figure A10 is used to determine how static corner weights change as you make adjustments
to the car. These adjustments include turning 'jacking screws' to adjust the preload on springs, changing
tire diameter/circumference, and moving weight around like ballast. Click on one of the 3 tabs at the top
to choose your option. The first tab, Jacking, is the same as it was in v3.2.
For most all inputs on this screen, click on the name or input box and its definition is given in the section
at the bottom of the tab page.
For the Tire Change tab, choose which tire to change and which dimension you want to work with. The
program will then display the Current Tire dimension from the Vehicle specs screen. You are allowed to
change this should it not be set exactly as you want. Then enter the New Tire dimension and see the
effect on Cross Weight. Rear and Left percents are not affected by changing tire diameter.
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For the Move Weight tab, choose the type of weight change, and the amount of weight to change. Then
type in the Current Location of the weight and/or the New Location of the weight after the move. Cross,
Rear and Left percents can all be affected by moving weight.
Click on Back (keep changes) at upper left of this screen to return to the main screen while keeping your
changes to corner weights, tire sizes, vehicle weight, etc.
Front Suspension Screen
Figure A 11 New Front Suspension Screen Features
New Table & Graph features are
explained in Figure A12.
Swing Arm Length and
Scrub are displayed here.
Figure A11 shows some of the new features for the Front Suspension Screen. Figure A12 shows an
example of the new “Table & Graph” feature for calculating Roll Center “migration” for various amounts
of dive and roll.
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Lt and Rt Scrub shows in Figure A11 is the amount the tire moves out from the center of the car as it
goes through the amount of dive and roll you have specified.
Lt and Rt Swing Arm Length is the distance from the center of the wheel/tire to its instant center. Long
lengths indicate that camber will change little with dive and/or roll (Camber Gain will be low).
Table & Graph
If you click on Table & Graph at the Front Suspension Screen, you will obtain a screen similar to to the
top picture in Figure A12. This screen shows you 2 tables of Roll Center Height and Roll Center Left
(distance left of center) for a set on Dive and Roll combinations. Distances right of center are labeled as
“negative”. (Negative in not “bad”, it is just a way to indicate right, the opposite of Left.) You could
have also chosen to do a Camber Table. Then the top table would be for the Right side and the bottom
would be for the Left side.
You can also select to have a Baseline condition displayed in the Table (Show Baseline Data). This is
useful to compare 2 different suspension layouts. A Baseline is some previous condition which was
shown in the Table.
To save the current Table as a Baseline, click on 'Baseline', then 'Save This Data as Baseline'. The
program will ask you for a Comment to describe the Baseline condition. This Comment will be printed
with the Table when you print it if you are Showing the Baseline condition. This comment can also be
edited by clicking on 'Baseline' and then 'Baseline Comment'.
After saving a baseline Table, you could close the Table by clicking on Back in the Menu Bar, make a
change in the suspension and create the table again by clicking on Table & Graph. You would produce a
Table like in the upper left of Figure A12.
Click on the Options menu item and select 'Specs for Table Rows & Columns' to change the Dive and
Roll increments, and which is used for rows and which is used for columns. You will obtain the menu
shown in the upper right of Figure A12.
As you change the specs in this menu, the Preview at the bottom changes to show what the Roll and Dive
increments, and the general layout of the Camber Table will look like. The program allows only up to 10
rows and 11 columns. Your inputs may be changed if a combination produces more than these limits.
When you are satisfied with the Preview, click on OK/Exit. Click on Cancel to close this menu and
return to the original Table layout.
Note: If you change the Table specs, any previously saved baseline conditions will be lost because that
baseline has different increments for columns and rows, which would not match up to the new increments
you have selected.
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Figure A 12 Roll Center Table and Graph
Click on Options
for screen to the
right to choose
increments for dive
and roll for table.
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Click on Graph to make graph
as shown below.
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Click on the Graph menu item and you can Graph the selected data from the Table. To select data,
you highlight various rows by clicking and dragging the mouse in the top Table for the Right Side.
These selected (highlighted) rows, AND the corresponding rows in the bottom table for the Left side, will
be graphed. If you have selected more data than the Graph can hold, you will be told and the top and
bottom rows only of what you’ve selected will be graphed.
This screen graphs of Camber in degrees on the vertical Y axis versus either Roll or Dive on the
horizontal X axis. The data graph here is based on what was highlighted in the Camber table when you
clicked on the Graph menu item. Data is always graphed for the Left side as well as the Right side for
whatever conditions you have selected (highlighted).
If you make graphs of Roll Center Height and Roll Center Left, as done if Figure A12, this graph will
show the actual location of the roll center and how it moves. Height is on the vertical Y axis and Left is
on the horizontal X axis.
Read the labels in the "legend" at the right side of the graph to see which lines are which colors. The
graph is always "autoscaled" which means the program picks the scales for drawing it to display all data
with good detail. Print the graph on your printer using your Windows default printer by clicking on the
"Print" menu command. You can change settings, labels and Windows printer setup by clicking on the
"Options" menu command. See Figure A13. You can return to the Camber Table screen by clicking on
the Back menu command.
Figure A 13 Graph Options Menu
The Graph Options screen is divided into 4 sections.
The first section is called "Graph Labels": Click on "Use Standard Labels" for standard labels to
be printed on the graph. Click on "Use Labels Given Here" and the program will use the labels
which you can enter or change. Click on any of the 3 text boxes and type in your chosen titles
or labels.
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The second section of the Graph Options is called "Print": Click on "Black and White" or
"Color" to tell the program how to print the graph. Unless you have a color printer, you should
choose "Black and White". The program always graphs in color on the computer screen. Click
on the "Print Now" button to print the current plot on the printer, the same as selecting the
"Print" menu command. Click on the "Windows Printer Setup" button to see the current printer
selection or select a different printer for printing the graph.
The third section lets you pick the line thickness for the "Plot Lines", either thick or thin.
The fourth section lets you pick the color for the "Background Color" of the graph, either black
or white.
Click on OK to return to the Graph Screen with your changes in effect.
Rear Suspension Screen
Figure A14 Symmetric, Angled 4 Link Rear Suspension
New Type is available of
Symetric Angled 4 Link
The new Suspension Type of Symmetric Angled 4 Link lets you find the roll center and roll stiffness of
rear suspensions found in several vehicles, including GM Metric and later model Mustangs. Because it is
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only for symmetric layouts, you will only enter measurements for 1 side, and they will be used for both
sides.
Engine Screen
Edit options have been added to the Calculate menu item to allow factoring the power curve up or down
by a certain percent. The option is also available to “clean up” the power curve should you enter RPM
increments out of order, or leave blank rows in the data.
Figure A13 New Commands in the Engine Screen
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Appendix 5: New Features in
Version 3.6
In Version 3.6 we’ve broken the Circle Track Analyzer into 3 different programs:
•
Roll Center Calculator (RCC), which does the Front Suspension only.
•
Roll Center Calculator Plus (RCC+), which does the Front Suspension and Rear Suspension,
plus some front to rear “balance” analysis.
•
The full Circle Track Analyzer (CTA), which does everything the old Circle Track Analyzer
v3.5 did plus all these new features.
Here is a listing of the major new features added in Version 3.6 of full Circle Track Analyzer. Note that
unless these new features specifically mention Roll Center Calculator, they do NOT apply to the Roll
Center Calculator versions.
•
The program now lets you enter a rear anti-roll bar. This input changes the front to rear roll
stiffness, which affects most all of the handling ratings the program will calculate. RCC+, CTA.
•
The program now lets you enter both a front and rear aerodynamic Lift Coefficient. Many times
when you make an aerodynamic adjustment, you only affect 1 end of the car, like a rear spoiler
adjustment. This adjustment not only affects overall “road holding” ability of the car, and
therefore lap times, it also affects handling, the tendency to oversteer or understeer. CTA only.
•
The program has a new Calculation Menu utility called “Adjust” for the front and rear Lift
Coefficient and Drag Coefficient. You can choose a type of vehicle modification, enter the
starting and modified condition, and the program shows you how the current lift and drag
coefficients would change. This way you have an estimate of how certain vehicle modifications
would affect the entire aerodynamics of the vehicle. CTA only.
•
You can now enter more details about the front suspension, both for Double A Arms and
McPhearson Strut suspensions. This added detail lets you locate both the front and rear A Arm
mounts on the frame, and the angle of the McPhearson Strut when viewed from the side. These
details let the program more precisely locate where the A Arm attaches to the frame in the 2
dimensional layout. They also determine how much Anti-Dive is built into the front suspension.
Anti-Dive is the vehicle’s resistance to diving the front end due to braking. Reasonable starting
points for Anti-Dive for most all circle track asphalt cars in the 2000-3500 lb range are 10% on
the Right Front and 5% on the Left Front. RCC, RCC+ and CTA.
•
We’ve taken the concept of balancing the Front Lateral Load Distribution (FLLD) with the rear
lateral load distribution a step farther. We’ve developed a Performance Trends exclusive called
Oversteer/Understeer rating. It is based on how evenly the tires on the 4 corners of the car are
loaded. If they are equally loaded left to right, and loaded front to back the same as the front to
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back weight distribution, we say that is a 0 Oversteer rating, or Neutral handling. Several
factors go into this rating, including banking forces, aerodynamic forces, dynamic weight
transfer left to right, and front to back. CTA only.
192
•
You can display the actual wheel loads for the car in “transition” on the track, at the point where
you are neither braking or accelerating. It is at this point where the program determines the
Oversteer/Understeer rating described above. For this “transition” condition, you can also save
a “baseline” condition for comparison to some modification you have made to the vehicle. This
way you can actually see the effect you modifications will have on wheel loads and the handling
rating. CTA only.
•
The oversteer/understeer rating is displayed as the car goes around the track on the Analyze
Suspension screen. By saving a condition as a Baseline, you can compare your current
conditions to a saved Baseline. This is the same as what is described in the preceeding
paragraph except it is done at all locations on the track. This is also the same as the “Analyze
Suspension” feature in previous versions, except now it includes the front and rear aerodynamic
downforce, and the handling rating. CTA only.
•
The ‘Rule of Thumb’ Suggestions for a good starting point for a setup now includes suggestions
for a “Big Bar Soft Spring” (BBSS) setup. The BBSS theory is you use significantly softer
front springs to better handle bumps in the track, and to lower the car in the corners for less
aerodynamic drag and less weight transfer inside to outside. Then to counteract the additional
roll these soft springs would allow, the anti-roll bar is stiffened significantly. Other adjustments
include a much stiffer than typical right rear spring, paying more attention to Anti-Dive and
shock valving. CTA only.
•
Improved the Tire Scrub calculation for a Double A Arm front suspension (how much sideways
tire movement there is during dive and roll). RCC, RCC+ and CTA.
•
Refined the calculations for suggested spring rates for “Starting Point Suggestions” report. CTA
only.
•
Program is now more compatible with Windows Vista and Windows 7. RCC, RCC+ and CTA.
•
Program is now better at remembering a printer or printer orientation changes. RCC, RCC+ and
CTA.
•
Program is now better at find newer versions of Adobe Acrobat and Reader, and other PDF
compatible programs for viewing the User’s Manual. RCC, RCC+ and CTA.
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Figure A15 Rear Anti-Rollbar
Roll bar drawn to
your specs here
in green.
Set to Yes and
you can enter
rear roll bar
specs.
Click here to
Calculate a roll bar
rate from other
inputs
You can also find a rear roll bar
rate to give a desired handling
rating (Front Lateral Load
Distribution, FLLD)
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Figure A16 Front and Rear Aerodynamic Lift Coefficients
Click on the
Adjust button for
the screen shown
below.
Program now has
both a front and
rear lift coefficient,
to split the
aerodynamic down
force between the
front and rear tires.
Height
Rear deck
of car
Angle
Length
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Figure A17 More Front Suspension Details
Enter both measurements for both front and rear
attachment points on frame.
The calculated 2-D mounting
point (used by program) is
shown here, with the current
2-D mounting point used by
the program from the screen
below.
Click here to use these new
2-D points in screen below
Calculated
Anti-Dive
Arrows showing front of car.
Click here on Show
Details button to open
screen shows above
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Figure A18 Oversteer/Understeer Rating
Dynamic Handling rating of 2.74%
Understeer, which includes cross weight,
aerodynamic, and other effects. Note that
this is completely different than the
“Classic” handling rating which only
considers lateral load (weight) transfer.
Click here to update the
“Dynamic Handling” rating and
to display the screen below
Aerodynamic Downforce loads for
both the front and rear axles (tires).
Also include are the loads for the
Baseline condition, a condition
which you have selected to be your
“Baseline” for comparisons.
Dynamic Handling Rating of Oversteer
or Understeer, including the rating and
difference between this and the
Baseline condition..
Check Section 3.6 in book “Analyze Suspension”
for more info on this screen. This “Dynamic
Handling” rating is for the vehicle at the “transition”
point, between braking and accelerating, no fore or
aft acceleration.
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Figure A19 Oversteer/Understeer Rating Around the Entire Track, and Big
Bar Soft Spring Starting Pont Suggestions
After you Calculate Lap Times, click on Analyze
Suspension for the screen below.
Click on Reports, then ‘Rule of Thumb’ Suggestions for
either a Std Setup or the new BBSS Setup. The program
will create the report like shown below with spring, roll
bar, stagger, anti-dive and other recommendations for
either type of setup you want to run.
Report is shown in Notepad so you
can easily copy and paste, email, or
print it on most any printer.
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Index
4 Link, 48, 179, 189
Accel Gs, 68, 98
Accel. Aggressiveness, 64
Acceleration, 68, 118, 119, 133, 165, 166, 171,
180
Active Bar Length, 87
Adobe, 192
Advanced file Open, 1
Aerodynamics, 21, 143
Air Temperature, 61, 62
Analysis Report, 66, 93, 95, 96
Analyze Perf, 5, 8, 66, 95
Analyze Suspension, 5, 8, 93, 116, 153, 161,
164, 174, 175, 192
Angle, 22, 23, 30, 33, 35, 36, 38, 42, 44, 51,
120, 157, 158
Anti-Dive, 191, 192
Anti-roll bar, rear, 191
Arm Len & Angle, 30, 42, 157, 158
Arm Length, 31, 87, 185
Aspect Ratio, 81
Assumptions, 6, 3, 7, 15, 16, 25, 36, 37, 46, 52,
66, 68, 72, 115, 118, 128, 139, 165, 167, 168,
171
Axle Ratio, 6, 127, 133, 135, 136, 143
Back Color, 105
Background Car Layout Color, 43
Background Color, 188
Balance, 191
Bank Angle, 24, 64, 90
Barometer, 60, 61, 62
Baseline, 8, 117, 118, 119, 127, 133, 162, 163,
171, 185, 192
Beginner, 13, 42, 57
Big Bar Soft Spring, 192
Brake Aggressiveness, 64
C.G., 76, 77
Calc Lap Times, 59
Calculation Menu, 5, 1, 9, 16, 70, 71, 87, 88,
142, 143, 144, 191
Calibrate, 138
Camber, 30, 37, 41, 43, 44, 46, 154, 155, 156,
157, 158, 160, 162, 173, 179, 185, 187
Camber Changes with New Inputs, 30, 43
Camber Does Not Change with New Inputs, 30,
43
Camber Gain, 41, 43, 44, 155, 156, 157, 158,
160, 173, 185
Car Length, 115, 118
CCs, 15, 74
Cd, 22, 23
Centerline, 27, 28, 29, 31, 32, 33, 34, 35, 36,
37, 49, 51, 52, 53, 54, 56, 120, 122, 168, 173
CG, 20, 121, 122
Chain, 21, 78, 79
Chain Drive, 78
Circle Track Analyzer, 1, 4, 6, 1, 2, 3, 4, 5, 11,
16, 17, 18, 25, 26, 41, 42, 57, 65, 66, 72, 90,
93, 96, 106, 107, 109, 110, 112, 116, 119,
127, 137, 138, 140, 144, 146, 149, 152, 153,
164, 165, 166, 167, 169, 170, 171, 191
Circumference, 26, 70, 80, 81, 179
Clc button, 70
Clc Button, 9, 15, 21, 25, 26, 35, 36, 38, 51, 54,
61, 62, 70, 74, 76, 78, 82, 83, 86, 87, 88, 143,
144
Clutch, 15, 16, 171
Coil Springs, 83
Comments, 5, 8, 16, 41, 47, 56, 57, 58, 71, 111,
119, 120, 139, 140, 145, 150, 151, 154
Continuous, 119
Corner Gs, 69
Corner Weight, 142, 179, 183
Corner Weights, 8, 20, 70, 75, 118, 141, 142,
168, 174, 179, 183, 184
Corr. Barometer, 60, 61
Current Run, 67
Cursor, 100, 101
Curvature, 68
Data To Graph, 98
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Dew Point, 9, 16, 61, 62, 87, 88, 89, 167
Differential, 78
Disabled, 44, 60, 61, 62, 71, 147, 157
Displacement, 15, 16, 73, 74, 75, 171, 172
Displacement in CCs, 74
Displacement in Liters, 75
Distance, 20, 21, 26, 27, 28, 31, 32, 34, 35, 37,
49, 51, 52, 53, 54, 56, 63, 64, 68, 74, 77, 80,
82, 85, 87, 98, 114, 118, 120, 122, 155, 170,
185
Dive, 36, 37, 39, 43, 44, 117, 154, 156, 159,
160, 162, 173, 185, 187, 191
Double A Arm, 28, 31, 33, 34, 35, 37, 44, 191,
192
Downforce, 23, 24, 118, 119, 130, 192
Drag Coefficient, 22, 24, 169, 191
Draw ‘Big’, 39
Driver, 64, 90, 147, 169
Dry Bulb, 9, 61, 62, 70, 88, 89
Dynamic Camber, 37, 159, 160
Dynamometer, 16, 169, 170
Elevation, 60, 62
Engine, 4, 5, 6, 12, 13, 14, 15, 16, 17, 18, 20,
22, 25, 27, 28, 49, 51, 52, 56, 60, 67, 68, 70,
71, 72, 73, 74, 75, 78, 79, 90, 91, 96, 98, 103,
106, 107, 108, 109, 110, 111, 113, 114, 118,
121, 127, 130, 131, 132, 133, 134, 138, 139,
140, 145, 150, 151, 165, 166, 167, 168, 169,
170, 171, 172, 173, 174, 175, 179, 189
Engine Analyzer, 15, 16, 17, 18, 103, 140
Engine Cubic Inches, 71, 73
Engine Graph, 13
Engine RPM, 68, 98, 114, 127, 130, 131, 132,
133, 134, 168, 170
Engine specs, 13, 14, 17, 72, 110, 139
Enter X & Ht at 1 End, Arm Len & Angle, 30,
33, 42
Enter X & Ht Readings, Frame & Ball Jnts, 30,
42
Examples, 5, 6, 5, 15, 17, 41, 42, 57, 71, 90,
125, 127, 138, 139, 140, 145, 153, 169, 171,
174, 175, 179
Extension Lines, 43
Circle Track Analyzer
Feet, 68, 98, 118
File, 5, 1, 2, 5, 6, 15, 16, 28, 41, 42, 47, 49, 56,
57, 58, 106, 107, 108, 109, 113, 127, 138,
139, 140, 145, 151, 154, 155, 174
Final Drive Ratio, 70, 78
Find Best Gear Ratio, 136
FLLD (Front Lateral Load Distribution), 179,
180, 181, 182, 183, 191
Flywheel, 15, 170, 171
Format, 100, 102, 104
Friction Circle, 64, 117, 118, 119
Front Pivot to Axle, 52
Frontal Area, 24, 25, 79, 80, 165, 166, 169, 172
Gear, 1, 19, 21, 25, 27, 49, 78, 79, 132, 143,
151, 170, 171
Graph, 1, 6, 8, 13, 15, 66, 97, 99, 100, 101, 102,
103, 104, 105, 112, 113, 130, 131, 132, 133,
174, 184, 185, 187, 188
Graph Labels, 187
Graphs, 5, 63, 67, 97, 100, 137, 147
Grid Style, 104
Gs, 68, 69, 98, 133, 135, 166
Height of C.G., 20, 21, 143, 168, 172
Help, 2, 3, 6, 8, 9, 13, 16, 41, 56, 70, 144, 154,
155, 175
Highest RPM Before Braking, 91
History, 5, 66, 98, 99, 112, 113, 114, 116, 133,
134, 135, 136, 137
Hollow, 83, 85, 86, 87
Humidity, 16, 61, 62, 70, 87, 88, 89
Improvement, 66, 67
Improvement Summary, 66
Include Vehicle Comments, 111
Include Vehicle Specs, 110
Inertia, 15, 21, 170, 171
Infield Width, 64, 90, 114, 162, 169
Install, 9
Installation, 5, 4
Instant Centers, 30, 43, 120, 159
J bar, 34, 35, 52, 54
200
Appendices
(C) Performance Trends Inc 1999
Circle Track Analyzer
Appendices
Jacobs Ladder, 54, 55
Number of Active Coils, 84
King Pin Angle, 34, 38
Know Dew Point?, 89
Know Relative Humidity?, 87
Obs. Barometer, 61
Open, 5, 15, 16, 22, 41, 42, 57, 106, 107, 127,
138, 139, 140, 145, 154
Open Example, 15, 16, 41, 57, 139, 140, 145,
154
Open Saved, 15, 16, 41, 57
Optimize, 23, 165, 173
Other Specs, 32, 33, 34, 35, 36, 156
Outside Air Temp, 87, 89
Outside Rel Humidity, 88
Oversteer, 180, 181, 191, 192
Lap Time, 5, 7, 26, 66, 67, 90, 91, 114, 115,
127, 130, 132, 148, 149, 150, 162, 164, 167,
169, 171
Lap times, 1, 20, 26, 82, 90, 91, 114, 117, 136,
138, 149, 153, 160, 161, 168, 169, 191
Last Run, 67
Layout, 27, 43, 50, 51, 55
Leaf Springs, 49, 52, 83, 84
Legend, 100, 102, 113, 187
Length, 30, 33, 38, 42, 44, 157, 158
Letter Tire Size, 81
Lever Arm Length, 85
Library, 5, 6, 106, 107, 108, 109, 138, 152
Lift Coefficient, 24, 130, 169, 191
Line Style, 104
Liters, 75
Load from Engine Analyzer, 16, 17
Lower Arm Angle, 33
Lower Arm Length, 33
Lower Ball Joint, 32, 157
Lower Frame Pivot, 29, 32
Lower Spring Pad, 32, 34, 36
Lower Strut Loc, 34
Lowest Engine RPM in Turns, 91
Main Menu, 4, 5, 6, 9, 11, 13, 17, 26, 59, 66,
82, 90, 107, 109, 127, 128, 132, 139, 149,
150
Match My Lap Times, 5, 82, 90, 91, 149, 150,
152, 169
McPherson, 28, 30, 33, 44, 45
Method of Reading Weather Data, 60, 87, 88
Milliken, 180, 181
Motion Ratio, 120
Move Weight, 184
MPH, 7, 66, 67, 68, 98, 115, 118, 127, 130,
132, 148
Natural Frequency, 121, 181
P Metric, 81
Panhard Bar, 34, 35, 52, 54
Panhard Bar Heights, 52
PDF, 175, 192
Peak HP, 71, 72
Peak HP RPM, 71
Peak Torque, 71, 72
Peak Torque RPM, 71, 72
PERFTRNS.PTI, 2, 4, 109, 127
Pinion, 27, 49, 78, 79, 143
Plot Lines, 188
Pnhd Bar to Centerline, 52
power curve, 16, 17, 18, 70, 71, 91, 139, 140,
150, 151, 179, 189
Preferences, 5, 13, 67, 179
Print, 5, 1, 2, 8, 16, 28, 31, 42, 47, 49, 57, 58,
66, 93, 100, 102, 110, 119, 185, 187, 188
Quick Change, 78, 143
Radius, 68, 77, 82, 120, 122
Rating Type, 80, 81
Ratio of Trans Gear Used, 25
README.DOC, 2
Rear anti-roll bar, 191
Rear Axle Ratio, 21, 78, 127, 132, 143
Rear Axle Type, 21, 143
Rear Suspension, 5, 1, 26, 48, 50, 51, 56, 57,
58, 83, 106, 109, 111, 120, 121, 138, 146,
150, 151, 174, 179, 182, 188, 191
Rear Track Width, 80
201
(C) Performance Trends Inc 1999
Registered Owner, 3, 4
Rel Humidity, 60, 61, 62, 70, 87, 88
Request Report Comment, 111
Roll, 1, 2, 11, 28, 30, 34, 36, 37, 38, 39, 41, 43,
44, 86, 87, 117, 120, 121, 122, 154, 156, 159,
160, 162, 168, 173, 179, 182, 184, 185, 187,
191
Roll Bar Rate, lb/in, 120
Roll bar, rear, 191
Roll Center, 1, 2, 11, 28, 30, 34, 41, 43, 117,
121, 154, 156, 159, 160, 162, 168, 173, 179,
182, 184, 185, 187, 191
Roll Center Calculator, 1, 11, 28, 41, 191
Roll Center Calculator Plus, 1, 11, 191
Roll Center Migration, 179
Roll stiffness, 38, 120, 121, 167, 189, 191
Roll Stiffness, 120, 121
Rolling Radius, 80, 81, 82
Roof Height, 80
RPM at HP Peak, 72, 73
RPM at Peak HP, 71
Rule of Thumb, 119, 122, 123, 179, 192
Running Conditions, 5, 24, 59, 67, 87, 88, 127,
128, 132, 147, 148
Safety, 3
Satchell (Terry), 180
Save, 1, 5, 16, 17, 41, 42, 57, 108, 109, 114,
151, 154, 185
Save As, 42, 57, 154
Scales, 103, 104
Scrub, 34, 37, 120, 122, 185, 192
Scrub Radius, 34, 37, 120
Sec, 67
Setup, 16, 100, 119, 144, 188
Shim, 41, 44, 45
Show Dive & Roll, 27, 38, 159
Single Step, 119
Spindle Angle, 34, 38, 44
Spoiler, 22, 23, 24, 191
Spring, 32, 33, 34, 35, 36, 37, 39, 51, 52, 53,
54, 83, 84, 120, 121, 154, 160
Spring Compressn, 160
Spring Deflection, 39
Spring Front Height, 52
202
Circle Track Analyzer
Appendices
Spring Length, 35, 36, 84
Spring Rate, 32, 33, 35, 36, 37, 51, 52, 54, 83,
120, 121
Spring Rear Height, 54
Spring Rear to Axle, 53
Spring to Axle, 51
Spring to Centerline, 51, 52
Spring Width, 84
Sprocket, 78, 79
Static Camber, 173
Static Layout, 27, 28, 34, 35
Stiffness, 38, 120, 121, 167, 189, 191
Straight Axle, 34
Suspension, 5, 6, 1, 8, 11, 20, 26, 27, 28, 29,
30, 33, 34, 35, 37, 38, 39, 40, 41, 42, 43, 44,
45, 46, 47, 48, 49, 54, 55, 56, 57, 58, 63, 66,
76, 83, 85, 86, 87, 93, 106, 109, 111, 116,
117, 119, 120, 121, 122, 123, 138, 144, 145,
146, 147, 150, 151, 153, 154, 155, 156, 159,
160, 161, 162, 163, 164, 167, 168, 172, 174,
175, 179, 182, 184, 185, 189, 191, 192
Suspension Calculations, 119, 120
Suspension Layout, 27, 30, 39, 40, 43, 44, 55,
120, 121
Suspension Library, 154
T Bar Rate, 36
T.Bar Arm to Centerline, 54
Tech Help, 3, 4
Test Results, 5, 17, 24, 65, 93, 98, 99, 112, 116,
117, 118, 119, 129, 130, 132, 133, 134, 136,
149, 161, 162
Thick Lines, 13
Thin Lines, 13
Tire Change, 184
Tire Diameter, 26, 80, 179
Tire Scrub, 179
Tire to Centerline, 49, 51, 52
Titles, 102
Torsion Bar Diameter, 85
Torsion Bar Length, 85
Torsion Bar Rate, 35, 36, 37
Torsion Bars, 35, 37, 54, 83, 85
Total Vehicle Weight, 76
Total Weight with Driver, 20
(C) Performance Trends Inc 1999
Track Length, 63, 137, 162
Track Weather, 60
Traction, 2, 25, 26, 68, 82, 90, 117, 118, 119,
144, 150, 160, 166, 167, 168, 169, 171, 173,
179
Traction Factor, 2, 26, 82, 90, 144, 150, 169
Trailing Arm, 49, 50, 51, 52, 54
Transition, 180, 192
Transmission, 15, 19, 25, 51, 78, 79, 143, 171
Tread, 26, 80, 81, 144
Tread Width, 26, 80, 81, 144
Truck Arm, 48, 50, 51, 52, 54
Turn #, 66, 67, 68, 118
Type, 16, 21, 22, 25, 28, 33, 34, 35, 41, 44, 45,
48, 49, 51, 54, 57, 63, 64, 78, 81, 83, 86, 90,
130, 143, 144, 147, 169, 189
Understeer, 180, 181, 191, 192
Upper Arm Angle, 33
Upper Arm Length, 33
Upper Ball Joint, 31, 33, 155, 156, 157, 158,
161, 162
Upper Frame Pivot, 31
Upper Spring Pad, 32
Upper Strut Loc, 34
Circle Track Analyzer
Appendices
Vehicle Library, 6, 9, 93, 106, 108, 114, 129,
138, 152, 153
Vehicle Weight, 20, 70, 75, 142, 171, 172
Version 2, 1
Vol Eff, 71, 72, 73
Weather, 5, 9, 60, 61, 62, 88, 89, 111, 127, 147
Weight %s, 70, 75, 118, 142, 171, 172
Wet bulb, 88, 89
Wet Bulb, 88, 89
Wheel Rate, 32, 33, 36, 37, 120
Wheel Rim Diameter, 82
Wheel/Tire, 25
Wheelbase, 21, 76, 143
Wheels & Tires Wt, 25
Wind Resistance, 22
Windows, 1, 2, 4, 5, 15, 16, 18, 22, 41, 42, 56,
57, 100, 109, 117, 119, 127, 140, 174, 179,
187, 188, 192
Windows Print Setup, 42, 57
Worksheet, 28, 42, 49, 57
X&Ht Readings, 155, 157, 158
203
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